Despite being enormous, manta rays eat some of the tiniest things in the ocean: plankton and tiny fish. They swim with their wide mouths open, filtering billions of microscopic creatures from the water as they glide along. It is the same idea as a whale shark - a very big animal eating very small things.
Manta rays are closely related to sharks - both are cartilage fish, meaning their skeletons are made of the rubbery material called cartilage rather than bone. But unlike many sharks, manta rays have no teeth for biting. They are completely harmless to swimmers and are famously curious, sometimes circling near divers as if inspecting them.
In Palau, manta rays gather at certain cleaning stations on the reef - places where small fish and shrimp remove parasites from the manta's skin. The mantas hover nearly still while the tiny cleaners do their work. It is one of the most remarkable teamwork partnerships in the entire animal kingdom.