by eating other fish
Fish don't have eye lids, so they never close. But there are exceptional fishes like the Sharks do have eyelids to protect their eyes!
To eat the other fish and protect their group!!
they kill other fish to survive and their eyes adapted to all of the majestic fish and blood everywhere from other sharks
Even though sharks are among very few fish which have eyelids, they do not blink. Most species of sharks have special nictitating membranes which go over their eyes to protect them when they are hunting or under attack.
They just know......
whale sharks,larger fish,barracudas
sharks
Sharks are carnivores, they can only eat other fish.
A fish that can blink with both eyes is the four-eyed fish. Although its name suggests that it has four eyes, it actually only has two eyes like other fish, but each eye is divided in two parts allowing it to see above and below the water simultaneously.
people, other fish, sharks and animals
sharks and other big fish eat rainbow fish