Davy Jones is a male humanoid of indeterminate species.
Human-like but able to breathe underwater, Davy Jones is a friend of Poseidon who owns a "dude ranch" at the bottom of the sea called Davy Jones' Locker. He is famous enough as a mythical entity at the bottom of the briny blue that "going to Davy Jones' Locker" has become a sailor's expression for going under, but in truth, Jones is far from being as threatening as this turn of phrase would imply, and lacks the "crew of ghostly seamen" that popular belief folklore has allocated him.
Behind the scenes
This version of Davy Jones was only ever seen in the 1953 story Bubbles, the Water Baby. The mythological character is also repeatedly mentioned in 1963's Lost Beneath the Sea, though Carl Barks was clearly not referencing the 1953 portrayal.
Considering his friendship with Neptune, ability to breathe underwater, fully human-like appearance, and mythical background in real life, it is possible that Davy Jones is actually a god as opposed to a mere human.