Unlike the pencil a diver has arms and legs that bend. Bending your knees bringing your fins up towards your head and extending your arms (getting into the skydiver position) is essentially moving your center of gravity.
Weight distribution (moment arm) and body position (center of gravity) need to be considered separately.
I really struggle to see your point ...
Indeed leg position / fin position shall be used to balance under water. Hence drysuit divers use negative fins, to allow themselves to play when the tanks becomes progressively lighter from the bottom mainly (top of the tank => regulator => very negative).
So basically:
- start of the dive: fins close to you to minimize the lever of action
- end of the dive: push the fins further (extend more your legs) to counter act the buoyancy swing (aka. tank butt up)
Arm's position has virtually no impact, the effect is totally marginal.
Put your arms in front of you:
- help with balance
- allow you to see your gauges (computer, compass, etc.)
- if you need to move your arm: body tension and fin movement will **temporarily** help.
Weight distribution (moment arm) and body position (center of gravity) need to be considered separately.
Absolutely NOT true. Weight distribution influence your "natural resting position". You can act on some factors, like the position of your fins but they are marginal adjustment variables. They are not how you properly "trim someone"
