The Ocean Sunfish (Mola mola) gets its common name from the habit of basking on the surface of the ocean, and its scientific name derives from the Latin word for “millstone”—the Mola mola is “the heaviest known bony fish in the world. It has an average adult weight of 1,000 kg (2,200 lb). The species is native to tropical and temperate waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal and ventral fins are extended” (source).
Molas aren’t simply big - they’re also exceedingly weird in terms of looks. “In the course of its evolution, the caudal fin (tail) of the sunfish disappeared, to be replaced by a lumpy pseudo-tail, the clavus. This structure is formed by the convergence of the dorsal and anal fins” (Ibid.). Milton Love, a Research Biologist at UCSB’s Marine Science Institute and author of Certainly More Than You Want to Know About the Fishes of the Pacific Coast (2011. Really Big Press, Santa Barbara ISBN 978-0-9628725-6-3), refers to them as “a Frisbee designed by Salvador Dali” and “a pelagic fish that has lost all semblance of dignity.”
“The presence of Mola molas off Southern California is not unusual, but the current number of sightings off San Diego, Orange and Los Angeles counties is extraordinarily high, perhaps explained by an abundance of sea jellies and unprecedented numbers of small, gelatinous creatures called Salps. Said Dave Anderson of Captain Dave's Dolphin & Whale Safari in Dana Point: ‘We are seeing both young and full-grown mola's on nearly every trip, and sometimes seeing 20 or 30 animals in a single trip, though often these are young ones. The mola sightings seem to have been improving along with blue whale, fin whale and minke whale sightings, and this has been one of if not the best years for sighting them’” (source).
Molas aren't listed as endangered, and they aren't commercially important (outside of Asia, particularly Japan, Taiwan, and the Philippines, where they are eaten), but little is known about them. “Pockets of mola researchers around the world have found that molas are powerful swimmers that buck ocean currents—dispelling a myth that they are lethargic drifters. Scientists are looking into what factors drive molas’ migrations, though one seems to be temperature. The fish prefer water ranging from 55 to 62 degrees Fahrenheit. Molas also dive up to 40 times a day. They descend to depths, on average, of 310 to 560 feet, most likely to forage in a food-rich zone called the deep scattering layer. Presumably to recover from temperatures as low as 35 degrees Fahrenheit at that level, they then sunbathe at the surface” (source).