Scuba Skills Review: Dealing with a Silt Out!
Getting caught in poor visibility can happen to any diver at anytime. Getting trapped in a silt-cloud is a serious example of this and can feel very unnerving as it is often impossible to see even your own hand when you wave it in front of your face. This zero visibility ‘silt-out’ creates challenges for divers and forces them rely upon other techniques to move around safely and try to get to better visibility areas. Even experienced divers can feel uneasy and sometimes panic when caught in a silt-out and it can create dangerous problems such as vertigo, buddy separation and rapid ascents or descents.
Silt is a very fine, light granular material. Because it is much lighter than sand, even the slightest disturbance can cause it to move. Silt clouds are most often created by other divers. Bumping and dragging along the bottom, finning too hard with the legs and fins pointing downward and shifting debris can all cause a huge billowing of silt. This silt cloud quickly expands and covers a large area underwater. It can be affected by water movement and currents to totally surround a group of divers causing chaos and disorientation.
Whilst most commonly found on the surface of the sea bed, silt also accumulates in enclosed spaces underwater, such as wrecks and caves. This causes even more issues as a silt-out in an enclosed space such as a wreck can be very dangerous, leaving the diver to have trouble finding the right way out.
Despite the problems that silt-outs can cause, getting caught in a silt cloud can be managed safely using some of the techniques identified below. Ideally, you will want to try and avoid silt clouds all together by practicing correct finning techniques, and maintaining proper buoyancy and trim when diving. If that isn’t possible however, it is important to be prepared and practice so that if it happens to you you can safely negotiate the correct course of action.
Carrying important equipment such as a powerful dive light, dive computer/depth gauge, dive line (a requirement for any wreck or cave penetration diving!) and a compass can make dealing with a silt out that much easier. Also accessorize your dive equipment so that you can be easily identified underwater, for example, bright yellow fins are more obvious than black fins!
It is easy to panic when you can’t see anything underwater. If you start feeling overwhelmed or panicked, the first step is to stop, breathe and focus. Closing your eyes and focusing only on your breathing can help you relax and slow your heart rate, reduce air consumption and help focus your thoughts on how to act next. Once you are calm you are ready to think and act to get away from the silt-out.
Hold onto your buddy
When you find yourself in a silt out, try to locate your buddy as soon as possible. It is very easy to lose track of where they are because of the bad visibility. If you can find him make sure to stay very close or even hold onto each other so that you don’t get separated. If you do lose track of your buddy in the silt out, follow a method below to exit the silt cloud and try to locate your buddy in better visibility. However if you do lose each other, be sure to follow the standard rule of looking for your buddy for no more than 1 minute, and then ascending slowly to the surface to reunite if you still haven’t located them.
Having zero visibility, it is easy to lose track as to which way is up and down. Establishing your orientation is important in determining which way you need to swim to exit the silt cloud. There are various ways to establish orientation:
Look closely at your dive computer or depth gauge to ascertain your depth. Try and stay at your current depth using neutral buoyancy to prevent any rapid ascents or descents.
Look and follow your own or a buddy’s bubbles - this will quickly show you which way is up towards the surface.
Look and feel for the the bottom or sea bed. Having contact with solid point of reference such as the bottom will give you a starting point and help you tell which way is up and down.
Look for any light parts of the silt cloud - often a lighter part of the silt cloud will indicate less silt in the water making visibility slight better, or the sun or a buddy’s torch shining through the silt.
Swimming correctly in a silt-out
When swimming through the silt cloud try to maintain good neutral buoyancy to prevent any surprise ascents or descents. When you start moving, try using the Frog Kick finning technique. This technique will prevent any more silt from getting kicked up which would make it more difficult to escape. When swimming, take your time and proceed slowly and gently. Because of the poor visibility you might not see what you are swimming into. Having your hand out in front of you will protect your head in case you bump into anything which may be hidden.
Try to ascend above the cloud
After establishing orientation, you can slowly and calmly ascent slightly to try and rise above the silt cloud (if you are in open water or have no overhead hazard). Depending on how much silt has been kicked up, the cloud might only be a few meters high. Using finning and good buoyancy practice, ascend slightly paying close attention to your computer/depth gauge to ensure you don’t ascent too quickly or too far - you don’t want to end up at the surface without doing a safety stop! Once above the silt cloud you can swim over it until you reach the end and then continue on your dive/locate your buddy if separated.
Follow your compass out
Trust your compass! Before diving check your compass to understand which direction at your dive site you can swim to get to safety if required. If you know which compass direction is a safe way to proceed, then set your heading and keep a close eye on your compass as you swim slowly through the silt cloud. For example, if diving in a bay, you know that South will take you out to the open ocean and north with take you shallower towards shore, set your compass North and soon you will be safely out of the silt cloud in a safer and shallower area.
Follow a line or rope
If you know that you may encounter poor visibility, you can attach a line to an entry/exit point and trail it behind you as you swim. This way you will have an easy route back through any silt outs, by following the line back to safety. When doing this however, be careful that you or your buddy don’t become tangled in the line, as this could lead to even more problems. When diving in any enclosed environment like a wreck or cave, you should always lay a line as you go so that you don’t get lost inside. If you lose track of the line in an enclosed space, try to identify any lighter patches of silt, which could indicate an entry or exit point into open water.
Ascend to the surface
If the silt-out is so bad that you just can't escape it, you can always end your dive by safely ascending to the surface making sure to complete any safety stops. Once at the surface you can see which way you need to surface swim to safely make it back to land/boat. It is never a bad decision to end the dive if you encounter serious problems like this, as you can always dive again another time, hopefully when the silt cloud has had a chance to settle and the visibility is a lot better!