It’s a reasonable question to ask, but it raises another— “do fish have eyelids?”
The short answer is mostly no. That, combined with their lack of eyebrows, are why fish are famously hard to read. How can you tell if a fish is being cheeky if they can’t wink?!
But if you think about the purpose of eyelids, it actually makes a lot of sense. We have eyelids to keep our eyes moist and to help clear away debris like a windshield wiper. Fish, however, don’t have the same need.
Some fish, like sharks, do have eyelids though. Not for blinking, or winking, but for shielding from debris mid-feast.
Some fish have an extra thick layer over their eyes that function similarly to glasses, helping to focus on different objects. Kind of like built in contacts!
Most fish though have a thin, clear layer over their eyes. It’s pretty similar to our cornea.