Even though a flipper doesn't look much like a human arm and hand, the bone structure inside is just like ours. Manatees are marine mammals, just like whales and dolphins. The manatee tail, called a paddle, doesn't look like a dolphin's tail, called flukes. Both paddles and flukes are used for locomotion through the water by moving them up and down. That doesn't mean that they don't have ears or can't hear.
Manatees have a pinhole on each side of their head that looks like a small dimple.
Even though they don't have big ears, they hear very well and can even hear higher-frequency sounds than we can.