Lil38:
Learning from small mistakes is a good thing. Lots of newbies (myself included) forget, and use the 'thumbs up' signal instead of the OK. It takes a conscious effort, and sometimes a reminder just before the dive. After the dive, review the tiny mistakes that were made.
Absolutely. It
is real easy to get confused in the beginning, and give "thumbs up" to mean "OK" or, "Wow! That's cool!". I don't know whether there's any acceptable way to "backspace" that; that is, to cancel the signal if you immediately realize you made a mistake, before your buddy starts reacting to what he/she saw as an "ascend" command...
The "thumbs up" signal, more than any other, is a command. Not a suggestion; not a question asking whether your buddy is ready to finish the dive; not an invitation to debate; but a command. Even if you don't understand why your buddy is signalling it, give a thumb back and ascend together. Find out why, safely on the surface.
OOA would normally be signalled by itself... you'd take care of the air sharing, then thumb for ascent. Unless, I suppose, if you were too far away from your buddy and were so bad off that you needed to do a CESA, or worse (emergency buoyant ascent)... though I'm not sure you'd be wasting time signalling at all in that case...
Lil38:
In my PADI class, the correct procedure taught was to indicate LOA (fist to your chest) then the thumbs up- then, you ascend together.
Here I'm not sure I agree... if you're low on air (that is, not needing to share air or go into other emergency procedures yet)
and want to surface immediately, there's really no need to signal "low on air" in most situations... just a thumb is sufficient. No debate. Though showing the "low on air" signal or your SPG somewhere along the line then would let your buddy know why...
jonnythan:
a command such as [...] "head that way"
I can understand where "head that way" (signalled how? Index finger? Thumb?) would be a command in technical diving. But, face it... in most shallow recreational diving, the dive isn't planned to such a degree that there is never any ambiguity. There may well be a time when you want to "discuss" with your buddy on the spot, which direction he/she wants to go. The standard signal for "which way?" is flipping your thumb from side to side... though I think that could too-easily be mistaken as the ascend command. How do you signal "which way"? And/or how do you suggest you go in a certain direction, not meaning it as a command?
jonnythan:
a command [...] needs to be replied to using the same signal to show that you understand and there is no confusion. If someone gives you the thumb, reply with the thumb, and begin your ascent immediately.
Yes. No need for an OK response... because that would imply your buddy could disagree. The thumb response is an acknowledgement that your buddy saw and understood your signal.
--Marek