Muddy Waters: Techniques for Low-Vis Diving

Call me a wimp if you want, but my enthusiasm for diving is proportional to how far I can see underwater. It is safe to say that, given a choice, many divers would prefer good visibility. However, sometimes you don’t have a choice; even when you try to avoid it, turbid water can sneak up on you.

That happened to me in the Galapagos Islands. Beautiful day, clear water and suddenly we encountered a wall of green. Instantly visibility decreased from 60 feet (18 m) to less than 3 feet (1 m). It even happens in Hawaii. On days when it rains heavily in the mountains you often get a brown-water line where mountain streams empty into the Pacific. Longshore currents whisk the muddy water down the coast, quickly overwhelming a number of popular dive sites. On rare occasions divers might be greeted by 100-foot (32-m) visibility when entering the water and before the dive is over be literally feeling their way back to the boat.

Many divers, especially those accustomed to clear water, become uncomfortable when faced with limited-visibility conditions. Even if you know that visibility is going to be less than optimum and have dived in those conditions before, it is easy to lose your way. So what do you do if you encounter turbid water conditions and become disoriented?

The first rule of any stressful diving situation is to remain calm — stop, think and act. Unless you are in immediate danger, cease all activity and try to relax — take controlled deep breaths and force yourself to exhale slowly and fully. Repeat this until the initial wave of anxiety passes.

Once under control, consider your options. Unless you have completed a limited-visibility diving specialty course, you may not know how to react to being disoriented in turbid water, but you have to do something.

Begin by checking your gauges — air supply, depth and bottom time. If you run low on air or are near your planned bottom time limit, surfacing may be the safest solution. However, in severely turbid water sometimes you may momentarily have difficulty discerning up from down.

The one sure way of telling is by observing a tiny amount of water inside your mask — it will always pool on the downside. So if water is accumulating anywhere other than in the bottom skirt of the mask, you are not right-side up. It may be necessary to let a little water into your mask to perform this test.

In most disorientation situations, a diver can tell up from down by observing the direction of his exhaled bubbles (photo 1). Bubbles will always float upward, except in rare cases when the diver is experiencing a downwelling current. I have observed this only twice, once at Costa Rica’s Cocos Island and again at Blue Corner in Palau. Downwellings are not uncommon at these venues but are rare most everywhere else. These situations do, however, confirm that watching your bubbles is not a completely fail-safe way to determine up from down.

When disoriented in turbid water, swim into the current to avoid being swept away from the area you are diving. Observe your exhaled bubbles to verify the direction of the current. The bubbles in photo 2 are drifting backward as they rise; these divers are swimming into the current as they should.

Swimming into the current helps you avoid ending up downcurrent from the exit site or far away from the boat. Going beyond the site while swimming into the current is not a concern; you can always drift back after surfacing.

In good visibility many divers do not navigate by compass except when finding a site such as a wreck for which they have compass bearings. Since the water is clear, natural navigation techniques usually work well. However, before descending I always take a just-in-case compass reading toward shore. That way, I’ll never get caught swimming aimlessly in the wrong direction if I become disoriented or lose my way. By following the compass heading eventually I will end up on shore.

Another good habit to form, even in good visibility, is checking the depth beneath the boat. Upon reaching the bottom when descending, take a quick glance at your depth gauge. And as you swim away take a compass heading for the anchor location. If turbid water moves in and you become disoriented, you’ll have two references.

In turbid water your gauges — depth, compass, timing device and pressure gauge — are your eyes. When you descend into turbid water or anticipate the possibility of worsening visibility, plan to follow a compass course throughout the dive (photo 3). Combine depth, time and direction to navigate the site and safely find your way back.

Due to the absence of references, a constant depth is challenging to maintain in turbid water. The best solution is keeping a close eye on your depth gauge. The divers in photo 4 are slowly ascending, constantly checking their depth gauges so they don’t exceed the safe ascent rate.

The buddy system also takes on renewed importance in turbid water. To avoid becoming separated, most buddies stay especially close when they can’t see beyond arm’s length. In zero visibility it is a good idea to maintain physical contact or use a short lead line — each buddy holding an end — to stay together.

If you become separated from your buddy listen intently for his bubbles and do a couple of slow 360-degree rotations while looking for your buddy’s bubbles and light beam before completing the standard lost buddy routine.

Divers who become disoriented in turbid water sometimes forget or intentionally omit the safety stop while ascending. Even when you are anxious about getting to the surface, it is still important to make a complete safety stop. Keep a hand on your buoyancy compensator’s inflation/deflation control and pay special attention to your depth gauge. Unless you are running low on air, complete the stop, followed by a slow, in-control ascent for the final 15 feet (5 m) just as you would in clear water.

Any diver, regardless of experience level, can become a victim of disorientation in turbid water. Remembering to remain calm, using your gauges — depth, time, compass and air — and not deviating from safe diving practices will eliminate the anxiety often caused by poor visibility.

Story by Lynn Laymon
Photos by Barry and Ruth Guimbellot