A bit of an FYI this one…
Fish do sleep. No eye lids though, so it’s hard to tell.
Sharks have eye-lids (scary-bitey-monsters that they are) but it is even hard to tell when they’re asleep as they have to keep moving to make sure they can breathe. Best to google it.
This is why gangsters are also called sharks and when they ‘off’ someone they say ‘sleeps with the fishes’.