Why do fishes keep their eyes open when they are sleeping?

Question

Why do fishes keep their eyes open when they are sleeping?

Answer 1

fish don't hav any eyelids so they just drift slowly in water through periods of time.

Answer 2

No eyelids.

Answer 3

More than from other signs, we understand whether a man is asleep or awake based on the fact whether the eyelids are blinking or session-closed. Such an inference is not possible with fish because they have transparent eyelids which are mostly kept closed, even when they are awake, as shields to protect the sensitive eyeballs.

A fish undertakes sleep either by suspending itself in quiet water or by resting on the floor bed or under logs or hard objects if it is current water.

Answer 4

Fish don't sleep.  They undergo periods of limited activity during which their muscles rest.