I WONDER - Do Fish Have Eyelids? Me Pregunto - Tienen Los Peces Párpados?

The video explains that most fish cannot wink or blink due to the absence of eyelids, meaning their eyes remain open even while sleeping. It describes how fish sleep by relaxing and slowing their movements, while their brains stay alert for danger. Sharks, however, have eyelids, but they do not close completely.

What is the significance of fish having their eyes open while sleeping?

Do sharks have eyelids, and how do they function?