Reducing the risks is an every day part of diving, this article explains some of the main risks to safety and what can be done to reduce them.
Control ascent problems
The biggest problem of buoyancy is the vicious circle. Ascend a bit and the air in your stab jacket or suit expands a bit. The expanded air is more buoyant, so you ascend faster, as you do, the air expands even more, so you ascend faster still, and so on. So, the later you leave it to correct positive buoyancy, the harder it is to get it back to normal - until the point where it's expanding faster than you can dump, then you can't avoid going to surface.
This can end in a 'bend'. The only way to avoid this is early correction. Keep your buoyancy neutral at all times. Never forget the fastest way of dumping is to breathe fully out. This gets rid of 2 - 4 litres and works at any angle of swim. This is equivalent to getting 2-4 Kg of extra weight in one second flat. The instant you realise you're going up a bit too much, make it a reflex, to exhale fast as your first immediate response and hold it out, at the same time go for the dumps. While dumping, you can slowly begin to inhale as buoyancy control is regained.
Unless there is some other form of pressure, air will only escape if the vent is uppermost, it is surprising how many new divers forget this and try to vent air from their shoulder dump whilst inverted. Make sure that you are vertical or near vertical when dumping air from vents at the top of the stab jacket.
Dive safely in a dry suit
Dry suits can be potentially dangerous due to the risk of uncontrolled ascent especially if the diver is inverted as there is no way for the air to get out. You must keep your buoyancy under control every second of the dive. Small corrections early are easy, large ones after unintended ascents are much more difficult to manage. The next most important thing is not to dive too heavily weighted. This makes you put too much air in suit or stab jacket.
An example: Ascending from 10m to 3m and the air expands over 50%. If you are weighted well with only, say, 10 litres of air in suit/stab jacket, then that adds only 5 litres more air to get rid of.
With 2Kg too much weight at the surface, you need 4 litres more air at 10m to be neutral. The same ascent from 10m to 3m will then add 50% of 14 litres, or 7 litres more air - an extra 2 litres to lose. This shows how being over-weighted makes the ascent spiral problem much worse.
If you get into an ascent spiral, your first priority is to get upright, exhale fast and dump air. If necessary undertake the emergency air mega-dump by pulling neck seal open. You will naturally get wet and cold but not bent.
Just as dangerous is to be too light of course. Remember you can lose over 3Kg weight of air breathed from single cylinder by end of dive. Without a shot line or reef to hold onto, you can't avoid missing stops and maybe get a bend. To get your weighting exactly right in your dry suit, get fully kitted up, and in the water with 50 bar in your cylinders. You should just float at eye-level and sink if you breathe out. Remember to add 2 - 4Kgs if you test yourself in fresh water and are about to dive in Sea water.
Control buoyancy in a dry suit
There are two schools of thought on how best to do this:
- The first method suggests that you use your suit just to get rid of squeeze, and then use your stab jacket to control buoyancy. The rationale here is that the stab jacket dumps faster than some dry-suit dumps and it can dump whilst the diver is inverted.
- The second method suggests that you use your dry suit exclusively for underwater buoyancy and leave stab jacket empty during dive. You only use the stab jacket after surfacing for floatation. The rationale here is that you only have one buoyancy control to think about and less chance of confusion in a panic situation.
The most popular method is method 2 i.e., do it all with your suit. The reasons being:
- There is a single way of dumping and inflating.
- Modern dry suit dumps are as fast as stab jackets, and have the neck-seal option in extreme cases.
- A good test of being correctly weighted in a dry suit is that just removing squeeze should get you fairly neutral anyway.
So, get your weight right and you'll find yourself automatically using method two in practice, even if you prefer method one in theory.
Safely reduce your air consumption
All new divers breathe heavy. This is well known and quite normal. Everybody knows too that feeling you have, when you let your buddy down by terminating the dive too early due to your high air consumption. The reasons for this are as follows:
- Buoyancy problems - too much pumping and dumping.
- Inappropriate weighting - too light and you have to work hard to stay down, too heavy and you have to work to stay up.
An over weighted diver will have to put extra air into a stab jacket or dry suit to maintain neutral buoyancy. By itself, this is insignificant compared to the amount of gas a diver breathes, but it will have a bad effect on your position in the water, tending to turn you upright. Swimming requires greater effort due to the unnatural angle in the water and increased water resistance.
- Anxiety - most new divers are anxious during a dive, this can double your rate of breathing.
- Hard work - for example, swimming too fast or against a current consumes too much energy and also builds CO2 levels which make you pant, resulting in more air usage.
- Poor finning - a poor finning technique such as a bicycle kick is inefficient and wastes effort.
The only safe way to use less air is to breathe normally, relax and use less energy; these tips are all aimed at reducing your effort in the water and any associated anxiety.
- Do not try to save air by breath-holding, skip breathing or deliberately breathing shallow, you run the risk of bursting your lungs, building up of CO2 levels and get a headache. Excess CO2 triggers panting too, which makes your air usage worse.
- Relax - this is probably the most significant factor; reduce anxiety by good training and lots of practice.
- Get your buoyancy right, maintain neutral buoyancy at all times, a simple way to do this is to stop finning and see if you ascend or sink, another method is get your buddy to look at your position in the water, you should be horizontal in the water. If your head is higher you are too heavy (trying to swim up), head down and you're too light (trying to swim down). Get your buddy to check you out. Maintaining neutral buoyancy will also reduce drag thus avoiding unnecessary effort.
- Get your weighting right.
- Slow down. Energy use increases massively (to the third power) with speed through water. Take it easy, see more by looking harder not swimming harder. Stop and look around a lot.
- Improve your finning technique; use strong, gentle strokes of the whole leg, taking each kick through to completion.
- Use your snorkel on the surface if you can.
- Do not descend if you are out of breath, e.g., after swimming to the shot line.
- Do not use your arms to swim; experienced divers use their legs almost exclusively.
- Gently pull yourself along on rocks or wrecks (with care) if possible - this is much more efficient than finning.
- Use currents when going with you, cheat them when against you - swim nearer seabed for less current, keep to shelter of rocks/wrecks where possible. Use a surge by floating with current and locking on as it reverses.
- Make sure your equipment is streamlined and balanced:
- Keep drag down as well as your swim angle, avoid carrying bulky items, being over weighted (thus over inflated), using big diameter cylinders, dragging goody bags etc. They all use energy.
- Keep your equipment balanced and fixed - a loose weight belt will often rotate round a diver's waist, pulling you off balance and making you work hard to stay balanced.
- Use buoyancy control to go up or down (e.g. shot line), not finning.
- Get the most efficient fins you can afford.
- Stay warm - use an appropriate suit and under suit for the dive.
Your level of general fitness will also effect your air consumption; the fitter you are the less air you will use as your cardiovascular system is much more effective and efficient. If you do fall into the 'not so fit' category, embark on a fitness campaign.
Buddy checks and below surface checks
Many an incident could have been prevented by a good buddy check, as divers get more experienced they sometimes get a little complacent, don't let this happen to you. Always do a full and thorough check.
Whilst checking your buddy, make sure that you will be able to recognise them underwater. Make a mental note of the colour of their fins, suit and tank etc. and any unusual items of equipment or markings. As many a diver will testify, it is all too easy (and most embarrassing) to follow another diver instead of your buddy. It is also a good idea to clearly write your name on your tank and your delayed SMB and SMB, so that you can be easily identified by other divers and your boat cover.
It is also good practice to do a bubble and computer check just below the surface and make sure everything is functioning as it should before you descend.
Avoid being lost at sea
You're more likely to be lost than drowned. It is incredibly hard to see a diver on surfacing, typically all you can see is a small black head. This is made far worse in big seas or poor surface visibility or when you have to look into the sun.
Increase your visibility. The coastguard recommends a collapsible bright yellow flag. These can be attached to the cylinder by elastic cords. Deploy it if the boat can't see you.
Also highly effective is a big delayed SMB. A brightly coloured hood is also recommended. If you have black hood, stitch cyclists reflective plastic strips to it.
A more expensive option is EPIRB - Emergency Position Indicating Radio Beacon in a small watertight box. This emits an international distress frequency radio signal and can be picked up by helicopters, boats, planes, and (the more powerful ones) satellites. It warns of problems and guides help to you. It also works in fog, darkness and in high seas.
An alternative method is to carry personal flares, however there are depth limitations on these and they expire after a given time.
A good skipper will count the divers in and out again and would never leave a site until all divers were accounted for, however mistakes do happen. If you are diving from an unfamiliar hard boat or a RIB, make a pact with another buddy pair that you will check each other in, prior to moving off the site.
Dive safely as a threesome
The main thing is to all agree how it will work before diving. The safest approach is for each diver to look out for both the others equally. If either goes missing for any reason, pair with remaining diver and follow the lost buddy procedure, both surfacing after one minute to check where the third diver is and raise the alarm if they have not surfaced.
The more common "buddy pair with one tagging along" approach is not as safe. The worst situation is not to have agreed how the threesome will operate before the dive. It is very common for one diver to go missing and the other two are tempted to continue to dive on based on the assumption that the third went off solo deliberately or "they can look after themselves". Whilst this often turns out OK, it sometimes doesn't, with fatal consequences.
Know when to use a surface marker buoy (SMB)
SMB's let the boat cover keep track of you and marks where you're surfacing, Use one always, especially on drift dives - unless:
- Wreck diving - It will get tangled, you never go far, and you can come up on shot line anyway.
- Lake diving with buddies and surface cover, and no boats on lake.
- Diving anywhere else where tangling may be a problem e.g., under piers, through arches etc.
- If there are some very strong surface currents you may find yourself being pulled along.
- If you are not using SMB for any reason, make sure you have a delayed SMB with you instead.
Don't be fooled into thinking that the RIB can follow your bubbles; this can be difficult in waves or where obstructions mean your RIB is some way off. It is even more difficult, if the buddy pairs go in different directions.
Deploy a delayed SMB properly
The sending up of delayed SMB towards the end of the dive is a common practice for today's diver. However, it is not without its risks and there are some potential problems associated with this process that need to be minimised.
We have all heard stories of divers being dragged into an uncontrolled buoyant ascent as a result of using a delayed SMB. Such ascents carry the risk of lung damage and decompression sickness, and can be dangerous. Typically, the diver starts to fill the delayed SMB, it is then released and the reel jams! The diver is pulled upwards, unable to release the reel and enters the vicious circle of not being able to dump air fast enough thus accelerating their ascent as the air in their BC and suit expands. They hit the surface like a missile. In some cases the buddy, whilst trying to slow their buddy's ascent is also pulled to the surface. The following tips will ensure this does not happen to you:
- Get yourself properly trained in using the delayed SMB and practice its use in shallow waters.
- Ensure the reel is wound with a little tension, too loose or too tight will predispose to jamming. Check your reel before every dive.
- Ascend to the highest point whereby you can deploy it safely for e.g., on top of the wreck.
- Always check the route to the surface in clear and there are no divers overhead.
- Never fasten the SMB to you when you deploy it. (It has been argued that you should never do this at any time with any SMB as it can get caught in surface craft or propellers etc.).
- Have a strong strap or cord and clip attached to reel housing and if possible tie it to fixed object e.g., a piece of wreckage prior to inflation. That way if the reel does jam, you can sort it out, without being dragged to the surface.
- If you cannot secure the reel to wreckage etc. the next best option is to wedge yourself so that if the reel does jam, you will be able to sort it out without ascending.
- Alternatively, tie the reel to the end of your buddy's reel so that if it does jam you can just release it on their reel and hope that theirs doesn't jam.
- Where possible, do not deploy the delayed SMB in mid water, better to deploy from the seabed or on the wreck etc. That way you do not have to worry about maintaining depth while you're deploying it.
- Be very careful to ensure that items of clothing or equipment (especially regulators) do not get caught up in the reel.
- Before you release it from the fixed object make sure the delayed SMB is fully deployed and on the surface or it may take you up as you release it.
- Aim to have the bag just full by the time it hits the surface, so at 10m approximate half fill it, 20m third fill, 30m quarter fill, 40m fifth fill and so on (Boyle's law).
- If you are worried about free flows fill it slowly with very short, gentle blasts of your octopus or use exhaled air to fill it. Be careful your regulator doesn't get caught up in it.
- Always keep the line taut thereby reducing the likelihood of getting tangled in it or it getting caught on surface craft.
- When winding in the reel take care to wind it evenly across the reel and not too tight.
Keep together on drift dives
Always use a SMB on drift dives and ensure that your buddy has a delayed SMB in case of separation. It is surprisingly easy to lose your buddy on a fast drift. Classically your buddy clings on to something to get a closer look and you get parted in a split second. Make sure you always use a secure buddy line or use the SMB line. Feed out more line and let your buddy (or buddies) hang on.
Descending down the shot line
After your entry from the boat and your 'OK' signal the next task is usually to get onto the shot line, in slack water this is a simple case of swimming to it. In current however, this may be much more difficult. Move fast after the entry and get lined up with the shot, swimming across the current if need be. Your buddy should be doing the same but look out for them and assist where necessary.
As a general rule don't descend until you get your breath back, although this is not always easy, especially if you have half a dozen divers approaching you.
When descending, do it naturally, avoid pulling on the shot as you may dislodge it from the wreck or site and your companions behind you won't thank you for it.
One of the most fundamental skills that every diver should know is how to navigate underwater. These skills are the basis for many of the things that divers need to be able to do during regular diving. Some skills are simple, like getting back to the spot you started your dive from e.g., the shot line. Some are more complex like finding a lost object underwater.
Underwater navigation can be made more difficult by poor visibility and currents; note that a moderate current of one knot will carry you about 30 metres in one minute.
The following tips may help:
- Do some back ground reading and understand the various shapes and features of the more common wrecks.
- Get as much information about the underwater terrain and dive site as you can. If it is a wreck, find out the direction in which the wreck is laying and where the shot line is in relation to it, e.g., mid-ships, stern or bow.
- Know where you are in relation to the shore by taking a bearing to the shore or exit point.
- Note the depth at the bottom of the shot line. Many land dwellers think of locations in two dimensions, underwater this can limit your navigational ability. If the shot is at 6m for example you know that you will need to be at 6m before you can find it.
- Use your compass, but be aware of the magnetic influence of wrecks.
- Get a feel for the terrain or wreckage immediately surrounding the shot line, understand its location in relation to the wreck by setting out in one direction for a short distance and then return to the shot, repeat in other directions. Extend the range as you feel more confident about your whereabouts.
- Follow natural lines; a ravine, a wall, the perimeter of a wreck, the kelp/sand border.
- Monitor your depth frequently; sometimes your ears are the first indication of ascents and descents. Lightness and darkness can also give an indication of depth but again it can be unreliable, especially if there are moving clouds in the sky.
- The depth contours usually lie parallel to the shore and ravines usually run from the shore out to sea.
- Avoid using currents to give you a sense of direction unless you are sure they will be steady throughout the dive. In some cases they can be unpredictable and confusing. Remember fish normally swim into the current.
- Sound - although divers cannot pinpoint a sound, they can tell if it is getting fainter or stronger.
- It is quite acceptable to leave markers on the seabed or the wreck, for example, place a few rocks together at the point in which you need to head home.
- Estimate your distance traveled by:
- Fin strokes
- Arm lengths
- Air used e.g., 10 bar
Bear in mind that these are fairly inaccurate at the best of times and made worse by stops en route, currents and changing depths.
Sand ripples. Note the steep side to shore
- Sand ripples on the bottom are normally parallel the shoreline. The steeper side of the ripple is the side closer to shore.
- At times your compass will advise one way and your instincts will another. Unless there are some very compelling contra-indications e.g., serious doubts about setting it right in the first place, always believe your compass.
- A long swim to the boat will usually be easier under water, because you can use your full fin stroke.
- A boat on one anchor will usually point not into the wind, and not into the current, but somewhere between the two, depending on the relative strength of each. As conditions change, the boat will change heading too.
If you do get lost
There are a number of techniques you can use to find your way back to the shot line, the wreck or exit point. Which option you take will depend on several factors e.g., the amount of air that is available, depth, decompression status or visibility.
- Swim in a square - mark your start point and swim in a square pattern, say 1 minute North, then 1 minute East or West etc. You could use other cues such sand ripples, depth or other natural lines. If your directions and distances are accurate and you allow for currents you should return to the start point. The square can then be repeated in different directions or made larger.
- The following options involve using a reel, which generally means you will have to swim back to the start point unless you can devise a method of fixing the end of the line so that it can become dislodged under a strong pull, for example, bury the line end under some rocks.
- Tie onto a start point with the reel and swim out then back in varying directions.
- Tie onto a start point and undertake a circular search pattern, widening the line after every full circuit.
- Ascend slowly, take a surface bearing and re submerge. Care must be taken with tissue codes and some divers treat as a second dive.
Getting safely back to the shot line
There are occasions where it may be mandatory to return up the shot line, for example, if the surface visibility is limited by fog, mist, heavy rain or high swells.
Divers should always carry a DSMB even on a wreck dive and deploy it if you move off the wreck to let the skipper know. If all the divers have them, the skipper may plan to lift the shot as soon as all the divers are down. Find out if this is the case! If not, you may wish to come back up the shot line. In very good visibility or a small wreck that has easy navigation points, getting back to the shot is easy. In poor visibility you may need to lay a distance line. Attach the end of line from second reel (keep the DSMB reel in case you have to cut loose and ascend without the distance line reel) to the wreck near the shot. Never attach it to the shot line itself in case the skipper does lift it. Reel out as the dive progresses and reel it in to get back to the shot.
Remember that is not always the best idea to return up the shot line, as the current builds up it can get very hairy clinging to the shot, in some cases it is better to 'go with the flow'.
Shore diving can be hazardous if you get caught up in currents, make sure you are fully aware of which way the current is running, how fast and what might happen during the duration of your dive. Ensure that on the homeward journey, you are swimming with the current and not against it. Also choose a sheltered shore, if the wind is coming from the sea you may run into problems of swell and being washed towards rocks etc. Make sure there is someone ashore to raise the alarm should you run into difficulties or fail to return on time.
Personal diving computers
It is essential to become fluent in the use of dive computers, read the manual and play with it at every opportunity. Get to know the meaning of every number and display icon without having to think about it. Use it as teaching aid - watch it and learn how diving behaviour affects the decompression obligation. Change your diving behaviour in future to lower it.
Diving after a break
If you are diving after a break, for example, winter, there are a number of thing you should do to maximise your safety:
- Make sure equipment is in test, cleaned and fully functional.
- Test your dry suit and Stab jacket for leaks.
- Check your weight - you may have increased or decreased your weight over the break and might have to adjust your weight belt.
- Review and practice your skills including rescue skills.
- Make sure your initial dives are shallow and easy.
- Use the pool to check out your equipment or buoyancy etc.
Learn how to handle panic
Panic attacks are extremely unpleasant and can be dangerous under water. Many divers have experienced panic at some time or other; even divers that have logged hundreds of dives. In any stressful situation you must:
STOP - BREATHE - THINK - ACT
To minimise these situations:
- Practice your diving skills until they become second nature.
- Plan the dives and follow your plans.
- Discuss your skills and concerns with your instructor or Diving Officer.
- Visualise possible problems and solutions before a dive.
- Never dive beyond your training and capabilities.
Be a good buddy
Exactly what makes a good (and bad) buddy is open to interpretation, however here are some common themes:
- Must be safe, i.e., have safety very high on their agenda and remain calm in a crisis. Being safe is a combination of having the right attitude, skills and knowledge.
- Must be reliable and dependable.
- Should be pleasant, caring, patient, helpful and understanding.
- Should have similar interests, expectations and objectives of the dive.
- Should have similar equipment for example, twin sets, Nitrox or computers, air consumption rates.