Turns out mammals and birds aren't the only warm-blooded creatures. This, ladies and gentlemen, is the opah, and it's blowing the science world away with the ability to warm its own body.
The opah, also known as the moonfish, is able to stay 7 degrees to 9 degrees Fahrenheit warmer than the water that surrounds it thanks to the constant flapping of its powerful pectoral fins. That may not sound like an impressive feat to you, but that's because you're a mammal and staying warm is all part of a day's work. For a fish, this is a big deal. There are only a couple other fish that can raise their bodies' temperatures, and they're predators like tuna and sharks. But those fish are only able to temporarily become warmer during hunting before they have to recede to warmer waters and bring their bodies back to normal.
The opah, on the other hand, is able to stay in cold water indefinitely, their bodies staying at a temperature that allows superior biological functions like cardiovascular endurance. The other fish that live in cold water aren't biologically able to move with the energy that the opah can, so this warm-bodied darling's got the clear advantage when hunting the fish and squid that make up their diet.
The opah lives in oceans all over the world, deep in their chilly depths.