Luvdisc

Luvdisc is a Water-type Pokémon from Hoenn region. It does not evolve into nor from any other Pokémon.

Pokédex description
Rendezvous Pokémon

''Luvdisc live in shallow seas in the tropics. This heart-shaped Pokémon earned its name by swimming after loving couples it spotted in the ocean's waves.''

Evolution family
Luvdisc is the part of a one-member family.