I often dive in areas where we are in mid-water during decompression stops or while navigating and swimming. Here are a few tricks to maintain depth:
1. Create an artificial horizon/instrument panel. Assume a head all the way back (in its natural range of motion), chest to knees flat, fins flat, position while pulling your arms up high at the shoulders to align them with your ears. Imagine Michael Phelps flip turning off the wall at the Olympics for streamlining or a freediver ascent position. Both these body positions are really slick. The only problem is you cannot see forward if you are looking down. So, pick your head up to look forward. Now, your hands are in the way. Open your arms wider from the needle or bow they are forming to be able to see, but do not drop them. You should be able to see your gauges and maintain a horizontal angle of attack. Last, make anti-silt/anti-damage kicking a habit so instead of flutter kicking like a swimmer or freediver, use a comfortable anti-silt propulsion technique.
2. Sight over your gauges. Instead of staring at your depth/time/direction information, look out into the water column. You should be able to easily reference your instrument panel. What depth is displayed on your gauge? Do you want to hold that depth or adjust up or down? Breathing is the key here. Don't let the challenge of "blue water" (or mud water/dark water) diving stress you. Relax and breathe with a deep inhalation followed by an immediate long, slow exhalation. Watch your gauge. Are you inhaling so deeply that you are rising? Or, exhaling so deeply that you are sinking? Learn to cycle your breathing just a bit to catch yourself before you sink or float. Slowly sip your gas and slowly blow it out. Don't fill or empty your lungs so much that the numbers change on your depth gauge.
3. When swimming, be mindful of using a good kick technique that will push water behind you. If your kicks push water upward or downward instead of behind you, you will find yourself swimming at an angle. This will challenge your breathing to compensate for the depth changes caused by your kicks.
4. Use the tools in your environment. Once you lock into a depth, don't clear your ears. If you begin to feel pressure in your ears, you know you are sinking below your target depth. Inhale deeper to rise. Reference your gauge. Once you are back at your target depth, concentrate on breathing to maintain it. Rising is a little trickier because your ears will be less helpful. Small pressure changes aren't as noticeable as a large pressure change when floating upward. Your gauge will be a better guide. Keep good team awareness. If your teammates are skilled at maintaining depth in blue water, they can be a pretty decent visual reference. Look for anything in the environment that can act as a visual reference. A large particle in the water, cloudy water below or above a thermocline or temperature gradient, bottom or wall features, anchor lines. Anything fixed that doesn't move or move much is nice. You can reference it if hovering or pick points to reach while swimming. If you have a distinct thermocline that is in the range of depth you are trying to hold, you can even use feeling temperature changes as a clue.
5. Minimize movement. If your feet scull at 0 degrees trim angle, but you can hold them still at 5 degrees feet down, why not adjust your trim to allow you not to scull? Trim doesn't have to be "perfect" it needs to be "good." Absent minded sculling of the feet can push you up or down. When you scull your feet make sure it is deliberate such as to create a little lift employing the backward kick or to maintain direction.
6. Practice holding completely still at safety/deco stops and practice navigating mid-water. Go to a safe training environment with still water such as a lake or quarry and practice, practice, practice until you find your personal style and tricks that help you easily maintain position.
While what I posted above seems like a lot, it really just comes down to TEAM (reference buddies and make sure they are comfortable and their gear is in place), BUOYANCY (breathe correctly and cycle breathing to aid in maintaining depth), TRIM (good body position and propulsion), EVERYTHING ELSE (reference compass, gauges, visual or sensory cues, and perform any task slowly). Breathing is the key.
much better depth resolution (10cm increments) so you can see if you are moving sooner.
