top of page

Just a Trim

Had a great conversation yesterday with someone about, among other things, the absolute importance of holding still.

Ask any diver at any level what they love about the sport and almost certainly some version of, "It's so calm and peaceful," will be early on the list of reasons. Floating weightless in whichever is one's preferred underwater environment is obviously what enchants so many of us all. And we all did our neutral buoyancy exercises in those first few days of confined water training.

Much is made of neutral buoyancy and one sees countless bickerfests about whether or not it's OK to train students, even very early on, on their knees.

That's not what I'm going to talk about, though. What I've been thinking about all morning is the second piece of the control puzzle. Trim.

It's all well and good to feel neutral, to actually think, “Well, I'm not going up and down too much.” But not actually being neutral can be disguised by a couple of tricks many of us never even noticed we started doing, but which get unveiled when true control is required.

Unfortunately the critical value of proper trim is only really stressed (or sometimes, lamentably, practiced or even understood) in some circles. I've even heard it decried as some sort of vain posturing. Cave divers certainly value it for environmental and even safety reasons, but there are plenty of cave divers with... shall we say... less-than-ideal trim. Same can both be said for penetration wreck divers.

"But it's the open ocean. There's plenty of room! It's easier to look around if I'm much more heads up. Why should I bother with that fancy, picture-perfect trim?" I hear you ask... and I'm so very glad you did.

Let's start with the obvious.

From a truly horizontal position comparatively little water needs to be displaced to move forward (or backward). Like a dolphin or a torpedo not only does one slice through the water more efficiently, but with a proper frog kick there is even a rest phase with each kick, with legs extended and toes pointed, when one continues forward propulsion without expending any additional effort. This translates to less work and, consequently, less gas usage.

I’m sure plenty of people will be happy to correct me if I’m wrong, but I remember this being described as the correct body position in the water by most Open Water manuals. Head slightly up to look around, legs straight to flutter kick from the hips. I haven’t straightened the doll's legs because this doll has just started a technical class. This (or worse) is what the majority of divers have developed as muscle memory.

Comparatively more water needs to be displaced for forward movement. The rest phase of the frog-kick is harder to enjoy due to the even-more-increased water resistance slowing you down (which is compounded when legs jerk back to starting position and slow you down even more). I don’t even include a back-kick arrow here, because it’s all-but impossible from this position and gets counter-productively over-compensated for. So you can only move forward, inefficiently, which means more energy and gas used.

That’s the obvious. And all to do with moving… now let’s talk about holding still.

Let’s assume this diver has a properly balanced gear configuration and exactly the right amount of lift in their wing and/or suit. Arms splayed and knees apart to widen their profile and balance them out. They are breathing normally and they stop. Without so much as flicking a fin-tip, this diver will enjoy not only true weightlessness, but will also be able to maintain perfect position both horizontally and vertically moving, ideally, not one foot in any direction.

As they inhale, of course, their buoyancy increases with the volume change… there is so much water pressing uniformly down on a wide, flat surface that it will take a few moments for the buoyancy shift to overpower the water resistance. By the time it does, the diver is already exhaling. And while they are shifted to being more negative with the volume change, there is so much water pressing uniformly up on a flat surface that it will… you get the idea. They aren’t going to move up and down substantially with normal breathing.

From this motionless, stable platform any communication, sight-seeking, task, failure management, or whatever is going to be far more easily and safely managed. When this position becomes muscle memory one no longer needs to expend any attention whatsoever on trying to hold still… you just do. In the overhead this is critical.

Now let’s take a look at, “But in open water there is plenty of room.”

Yeah, it’s OK-ish trim. Probably better than average; it isn’t impossible to hold perfect position from this trim, but it is far harder than it either seems or is worth the effort. Because with this “that’ll do” trim there are a couple of problems illustrated by some confusing arrows.

When this diver stops completely and tries to hold position the buoyancy shift as they breath is more exaggerated. Because the water is now no longer pushing evenly down on a wide, flat surface, but rather a sloping surface. As they inhale it will take less time for them to start to move up through the water. Plus, due to the sloping surface, they also move a little bit forward.

There is good news… sorta. As they exhale they will start to drop in the water column. But they will also drop a little backwards. What most divers do, as they sense themselves dropping, is kick to maintain depth… which moves them forwards. (That’s the little red arrow.) So it winds up being not very good news because the see-saw doesn’t quite balance itself out.

The way this most commonly manifests is as someone is trying to stay in one place they start to inch forwards until they are so far past the point they were trying to maintain the only solution, with a back-kick near impossible, is to swim around in a wide circle back to their starting point. In the overhead this may not even be a safe option, potentially turning what might have just been a nuisance into a major goddamn catastrophe. Lost orientation or lost line or lost visibility or contact with something that reeeeeeealy shouldn’t be touched… take your pick.

In open water, at the very least, it means more energy and consequently more gas used. It also means you can’t hold still to look at whatever it was you were trying to look at.

It’s these problems that students frequently have trouble overcoming in technical classes with sometimes years of muscle memory to unlearn. It’s these same problems that, say, a photographer has trying to hold position while taking a picture of a nudibranch.

The way these problems are all-too-frequently overcome is by grabbing onto something which may or may not be a safe option.

The other trick divers lean on to overcome these problems is by using a wing-effect and never stopping moving. If you’re swimming into flow or current, or simply always swimming it’s all well and good to be proud of never changing a foot of depth with the illusion of control.

Perhaps the most commonly used and seemingly effective trick to hide crap buoyancy/trim is to breathe from the “top of the lungs.” That is: by maintaining a little more air in the lungs than a normal breath.

The biggest danger here ESPECIALLY in open water: a diver isn’t truly neutral, but depends on having a big breath in their chest to maintain depth, they exhale… and inhale against a dead regulator… and start to descend with nothing to fill either their lungs or BC… and, potentially, descend and descend and descend and descend… And this is to say nothing of a planned decompression stop in open water with crap buoyancy/trim, dangling off a lift bag like a testicle, or swimming circles around the diver with the lift bag when a failure happens.

So, yet again, your open water instructor lied to you. Perhaps they didn’t even know they were doing so, they were repeating back the same pablum they were taught, like that Napoleon was short, there’s a map of your tongue, or that the moon landing was not staged by anti-separatist Basque chefs. If they even used the word trim, a little bit heads up is not the right body position.

If you try to stop completely in the water and either don't stop completely or need to keep moving some part of your body to try to stay stopped: maybe it requires a bit of gear and/or weight tweaking to get properly balanced, maybe unlearning muscle memory, maybe some gas-space management technique, maybe just a little bit of coaching.

In any case, it really is worth it. That “tech diver” position is not just to look cool. It actually serves a valuable function for safety, comfort, effort, and even enjoyment of a dive.

It does also look cool. Aim for truly horizontal; look cool.

Recent Posts

See All


I'm starting a new class. Sort of. Not a prerequisite class... not exactly... though sometimes it will be useful as a prep curriculum. Not a remediation class... not exactly... though some people may

Don't Wear Fancy Pants

Yesterday, while single-tank sidemount diving in a 3mm shorty at the tips of the finger reef at 40 feet, the biggest Eagle Ray I've ever seen came cruising by the sandy wasteland of the desert boundar


Dirty Confession: When I'm moving painfully slowly through an area of cave which is heavily restricted and heavily decorated - such as if I am following a diver who is picking their way through carefu


bottom of page