Giant manta ray (Manta birostris) and fish. Manta rays were once called devilfish by sailors who saw large "horns" extending forward from their heads. These horns turned out to be ingenuous scoopers which are used to guide plankton into the manta's mouth. Manta wingspans can reach up to 20 feet, allowing them to glide though the water like birds. Both gentle and graceful, they have become a favorite attraction for divers.