Adult ocean sunfish are found in temperate and tropical oceans across the globe. They prefer the open ocean but occasionally venture into kelp beds and deep coral reefs in order to be cleaned of parasites by fishes such as wrasses (Labroides dimidiatus and Thalasoma lunare) and Emperor Angelfish (Hutchins, 2004; Humann and Deloach, 2002, Konow et al., 2006).
The scaleless body is covered with extremely thick, elastic skin. The caudal fin is replaced by a rudder-like structure called 'clavus'. Dorsal and anal fins very high with short base; in swimming, these fins are flapped synchronously from side to side and can propel the fish at surprisingly good speed. Pectorals small and rounded, directed upward (Ref. 6885). Mouth very small; teeth fused to form a parrot-like beak. Gills 4, a slit behind the last; gill openings reduced to a small hole at the base of the pectoral fins.
It often drifts at the surface while lying on its side, or swims upright and so close to the surface that the dorsal fin projects above the water. Sometimes reaches depths of up to 300 m (Ref. 9317). Feeds on animal plankton, eel larvae, small deep-sea fishes; also on jellyfish, crustaceans, molluscs, and brittlestars (Ref. 4925). In Guiness Book of Records it was recorded as the heaviest bony fish and as the one with the most eggs (Ref. 6472). Also occasionally caught with encircling nets (Ref. 9119) and harpoon (Ref. 9988). Mola is the latin word for millstone.