Manaphy is a small, blue, aquatic Pokémon. It has stubby feet and club-like arms that are longer than its body. Manaphy has a red gem on its chest, and a yellow dot below the gem. Manaphy has an onion-shaped head with a pair of long blue antennae, which have small spheres on the end. Manaphy's irises are dark blue, although the outermost portions of its eyes are yellow, with two eyelashes on each eye and yellow dots on the tips. Eighty percent of Manaphy's body is made of water and is highly susceptible to its environment. One of these reactions is that when Manaphy reproduces in an ocean that's warmer than those that they are native to, the child will be a Phione as opposed to another Manaphy.
Although Manaphy's Pokédex number appears after Phione's and Manaphy can breed with a Ditto to produce Phione, Phione does not evolve into Manaphy.
Manaphy has ability to exchange soul of a person.
Manaphy is known as the "Prince of the Sea". In Pokémon Mystery Dungeon: Explorers of Time and Explorers of Darkness, the Manaphy that appeared was referred to as a male however Manaphy are technically genderless.
Manaphy is the only mythical that can breed.
When it breeds with a Ditto, they make a Phione, Phione can also breed with a Ditto, another Phione will be produced.
Phione is technically Mythical or Semi-Mythical however this status has been heavily disputed due to the ability to have a lot of them on the same saved game without cheating, hacking or trading and Phione's stats are lower than most other if not all other Mythical and Legendary Pokémon, this status is even disputed between official sources.