All I'm gonna say is that it better be a real emergency. God forbid that system gets used for anything else. If ops started using that for routine "time to end the first dive" stuff, I'd compelled to swim over and start drilling holes in the bottom of the boat. That's worse than a 2 a.m. car alarm.
To OPs question, there's a thread right now about somebody who got their SPG chomped by a giant clam and was stuck, (which is AWESOME, btw). Moral of the story is "you just never know."
Make all the basic skills muscle memory and easy, then be mentally prepared to adapt. Learn to stay calm, assess, and act. Anything other than catastrophic unexpected OOA, you're gonna have time to deal with it. Just don't make it worse. Visualizing "what ifs" helps a lot.