Water is the least forgiving editor. Every input a diver sends down is returned unchanged: a tense hand becomes a jerky fin kick, an impatient rhythm becomes a cloud of stirred sand, a relaxed line through the water becomes exactly that. Nothing is exaggerated and nothing is hidden.
On the shark dive this was impossible to miss. The animals move with an economy that makes human propulsion look like effort, and the water carries the difference straight back. You learn to stop correcting from the shoulders and start letting the fins finish their sentence.
Buoyancy is the same bargain in slow motion — add air, rise; release, settle — a contract with no small print. What the water reports, finally, is not skill but honesty of input. Move cleanly and it says so. Rush, and it repeats that too, at full volume.