How Do Manatees See Underwater?

Just like sloths have poor eyesight, manatees also have poor eyesight — if a manatee took a human eye test, it would be classified as legally blind. So manatees also have another way to navigate in the sometimes murky water to find tasty plants to eat. Fortunately, manatees have no natural predators, so they don’t need to keep an eye out for dangers.

Like a sloth uses its nose to find food, a manatee uses its sense of touch. Manatees are covered in whisker-like hairs, which trigger nerve impulses in response to pressure changes in surrounding motion. Manatees also use ultrasound frequencies to communicate, and most likely use their kinesthetic sense to detect low-frequency sounds which also help them orient in their environment.

What would it be like to close your eyes and feel your way through your day? Manatees have a unique way of navigating their watery world, taking advantage of senses that are most useful, just like a sloth uses it’s sense of smell in the high-canopy world of the jungle.

Source:
http://animals.howstuffworks.com/mammals/manatees-see-underwater.htm