He is an anthropomorphic tuna fish, almost mermaid-esque in appearance, although far more grotesque.
He was created by Baron Dante's magic that made a fish (a tuna, according to concept art) into a trident-wielding demon.
Method of defeating
Neptuna is arguably one of the most challenging Guardians to defeat, likely because his battle (as well as the entire level) takes place underwater. Neptuna has two main attacks: tail swiping and shooting magic. He almost always tail swipes, only shooting magic once after the second time he is injured. As a result of his fishy origins, he has a very spotty memory and, after attacking, will have a brief memory lapse. Croc must swim up to him during this moment of confusion and tail attack him in order to inflict damage. Due to the underwater nature of this level, Croc moves much slower than when on land, and it is harder to avoid Neptuna's attacks. For this reason, it is very useful to stock up on crystals before entering the arena.
- His name is a playful combination of the name Neptune, the Roman god of the sea, and tuna, a kind of fish.
- The fact that he loses his memory briefly during the battle is based on the untrue myth that fish have a memory of seven seconds.