Fish have no eyelids, so they sleep with their eyes “open”. This Black-Saddled Toby (Canthigaster valentini) from Amed, Bali, Indonesia, found himself a shelter on a brown sponge to stay for the night. You will find plenty of fish on the same condition on your night dives. They will allow you to stay closer and shoot, and most won’t be too upset with your focusing light and strobes.
Take your chance but be respectful. Resist any impulse of touching, moving them or getting too close. Some fish (namely the parrot fish) produce a cocoon of mucus for protection against predators, and, once disturbed and woken up, won’t be able to produce another one for the same night.