8 animals that don't close their eyes while sleeping

Fish: Lack eyelids. Most sleep with eyes open, remaining vigilant. Some species rest half their brain at a time.

Snakes: Have transparent scales called spectacles covering eyes. They're always "open" but protected during sleep.

Geckos: Like snakes, have transparent eye scales. They lick their eyeballs to keep them clean and moist.

Sea lions: Can sleep with eyes partially open underwater. They're able to rest half their brain at a time.

Frogs: Have a transparent third eyelid (nictitating membrane) that protects eyes while allowing them to stay alert.

Dolphins: Sleep with one eye open, alternating brain hemispheres. This allows them to surface for air and watch for predators.

Whales: Similar to dolphins, they keep one eye open and half their brain active while sleeping to surface and breathe.

Crocodiles: Have a third eyelid for protection. They often sleep with eyes slightly open to remain alert for prey or danger.

This information is not DNA's opinion but obtained from media reports