5 Trim and Buoyancy Faults I Still See in Tec Students After 20 Years

You'd think that by the time a diver walks into a Tec course, trim and buoyancy are settled. They're not. They're just less obvious — which is worse, because nobody's flagging them anymore.

Here are five faults that survive well past Open Water and Advanced, and still show up in candidates who've logged hundreds of dives.

1. "Good enough" horizontal trim that isn't actually horizontal

Most divers think they're flat. Filmed from the side, a lot of them are 10–15 degrees head-up, feet-down — enough to disturb silt on a wreck penetration or waste finning effort on a long swim. It doesn't feel wrong because it's been "good enough" for years of recreational diving. It stops being good enough the moment you're in an overhead environment or managing a stage bottle.

Fix: Film your students from directly behind and to the side. Don't describe the correction — show them the footage.

2. Buoyancy control that relies on the fins, not the lungs and wing

Divers who spent years finning to hold depth (rather than breathing and trimming their wing) bring that habit into Tec diving, where it becomes a real problem: constant finning near a wreck or reef stirs up silt and burns gas you don't have spare capacity for on a long deco obligation.

Fix: A hovering drill with fins completely still — hands off the fins, literally — for 60 seconds at depth. It's humbling for a lot of "experienced" divers.

3. Overcorrecting with the wing instead of breathing first

Small depth changes should be managed with breath control. Instead, many divers add or dump gas from the wing for every minor fluctuation, which leads to a yo-yo pattern and delayed reactions, since wing adjustments lag behind breath adjustments by a couple of seconds.

Fix: Teach breath-first buoyancy explicitly, even to divers who "already know how to dive." Most were never taught this distinction — they arrived at decent buoyancy by trial and error, not by understanding the mechanism.

4. Task-loading collapse

Trim and buoyancy that look fine on a calm, no-task dive fall apart the moment a diver has to deploy an SMB, manage a stage, or handle a light. This is the fault that matters most for Tec certification, because task loading is the entire point of the training — deep dives with multiple gas switches and long stops are task-loading by design.

Fix: Build trim/buoyancy checks into every skill drill, not as a separate module. If a skill degrades trim, the skill isn't done yet.

5. Compensating with weight instead of fixing the actual imbalance

Overweighted divers often "fix" trim by shifting tank position or adding trim weights, when the real issue is simply carrying too much lead to begin with. This compounds gas consumption and makes the diver less streamlined overall — exactly the opposite of what Tec diving demands.

Fix: A proper weight check at the start of every course, no exceptions, even for divers who insist they're already dialed in. Most aren't, and most are pleasantly surprised by how much lighter they can go.

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None of these are exotic. They're the ordinary, unglamorous stuff that separates divers who look competent from divers who actually have the margin to handle things going wrong at depth. Worth revisiting even with your most experienced students.