Why do fish sleep with open eyes?

Fish don't actually sleep in the same way that mammals do. They don't have eyelids, so they can't close their eyes. Instead, they enter a state of reduced activity and responsiveness, often called "resting" or "dozing."

Here's why they keep their eyes open during this resting state:

* Lack of Eyelids: Fish don't have eyelids, so they can't close their eyes.

* Constant Vigilance: In the wild, fish need to be constantly vigilant for predators and food opportunities. Keeping their eyes open allows them to react quickly to danger or opportunities.

* Oxygen Intake: Fish get oxygen from the water through their gills. Keeping their eyes open allows them to maintain a good flow of water over their gills for oxygenation.

So, while fish don't sleep in the same way we do, they do enter a state of reduced activity and responsiveness, and they do it with their eyes open.