If a diver comes upon a rocklike objectat the bottom of the ocean, how would he tell if it was a living thing?

Question

If a diver comes upon a rocklike objectat the bottom of the ocean, how would he tell if it was a living thing?

Answer 1

Observation.  Just watch it! If it moves, blinks or twitches, it's alive. :)

Just remember, don't touch anything underwater.  Take nothing but pictures, and leave nothing but bubbles.