Other divers are often the reason for silt getting kicked up. These divers are known as ‘silt-miners’ — Other divers are often the reason for silt getting kicked up. We call these divers ‘silt-miners’. Try not to be a silt miner!

Getting caught in poor visibility can happen to a diver at any time and getting trapped in a silt-cloud is a serious example of this. It can feel very unnerving - 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 to use new techniques to move around safely. 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/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, and pointing fins downward can all cause a huge billowing of silt. This silt cloud can quickly expand and cover a large underwater area. It can also be affected by water movement and currents to totally surround a group of divers causing chaos and disorientation.

Silt-outs in enclosed spaces are not fun!

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.

Be Ready

Colorful Drysuits help identify you underwater in poor visibility!

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 altogether by practicing correct finning techniques, and maintaining proper buoyancy and trim when diving. If that’s not possible then it’s important to be prepared 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 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!

Stay Calm

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, slow your heart rate, reduce air consumption and help focus your thoughts on how to act. Once you are calm, you are ready to think and ready 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’s very easy to lose track of where they are because of the bad visibility. If you can find them, make sure to stay very close and 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 the method below to exit the silt cloud and locate your buddy in better visibility.

Establish orientation

Having zero visibility, it is easy to lose track of up and down. Establishing your orientation is vital to determine the 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.
If you can, find your buddy’s bubbles and follow them - this will quickly show you which way is up (bubbles travel up).
Look and feel for the sea bed. Having contact with a solid point of reference such as the bottom will give you a starting point and help you determine which way is up and down.
Look for any light parts of the silt cloud - a lighter part of the silt cloud can mean less silt in the water or can be the sun or a buddy’s torch shining through the silt.

Swimming Correctly in a Silt-Out

Good bouyancy and Frog kicking helps prevent any more silt getting kicked up

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 prevents 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 - it’s likely you may 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 ascend slightly to try and rise above the silt cloud (if you are in open water and 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 the direction of your dive site so, if required, you know which way to swim out of trouble. Understanding your orientation will allow you to swim safely out of a silt cloud. For example, if you know South will take you out to the open ocean and North with take you shallower towards the shore, you can set your compass North and soon you will be out of the cloud in a safer and shallower water.

Locating and following a reference point such as a line or rope, can help direct you out of the silt

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. When doing this, be careful that you or your buddy don’t become tangled in the line. 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 - 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!

As with most things, you can prepare and improve your low-visibility diving by practicing. Find a safe dive site and a safe depth where you can kick up a silt cloud and practice navigating and swimming through it using the techniques above.

The bay at our local dive site, Whytecliff Park, is ideal for this and you can come along on one of our club dives which will give you a chance to practice under the supervision of our Divemasters.

Scuba Skills: Dealing with a Silt Out