The term sea devil is often used in reference to the manta ray, a large species of jawed fish that is related to the shark. Sea devils are the largest species of ray, capable of weighing more than 5,000 pounds (about 2270 kg) and growing longer than 25 feet (7.5 m) across. These fish eat as they swim, catching larva, plankton, and other small prey in their gills, and they are found around the world in tropical waters. A sea devil is normally not kept in captivity due to its extraordinary size, but some of the largest aquariums in the world occasionally keep them after the fish are accidentally caught. The term sea devil also occasionally refers to the family of rays in which the manta ray belongs, known as eagle rays.
Sea devils in general, including other members of the eagle fish family, are normally quite large, but some can be little more than 1 foot (0.3 m) long. These fish appear relatively flat with long wings and a slender tail with a length that depends on the species. The color of their bodies also depends on the species; some are a mostly solid gray, while others are spotted or sport other patterns.
A sea devil from the eagle fish family can give birth to up to six babies. Some species typically deliver very few. For example, the manta ray gives birth to one young at a time. In the ocean, both young and adult sea devils are vulnerable to attacks by sharks of similar or greater size.
While rarely found in captivity, there have been a few instances of these fish being housed in aquariums. In at least one case, a sea devil was accidentally captured in a shark net, and this led to it being transferred to an aquarium. One sea devil has been born in captivity at least once, though this is a very rare occurrence due to the very low number of sea devils that are in aquariums. There is a limited number of aquariums that can even support a sea devil due to their extreme size.
Little is known about the locations that some species inhabit, but sea devils of most species are known to frequent warm waters and coral reef areas. These fish are sometimes seen by divers, often around coral reefs, and are typically indifferent to humans and not aggressive. Due to their slow breeding habits, the sea devil is believed by some organizations to be threatened as a species.