More 5th Gen Pokemon

The Mermaid Pokemon
Seareen
Water/Normal
Ability: Serene Grace or Marvel Scale

The beautiful (and always female) Seareen, are as close to actual mermaids as anyone will ever get. With a humanoid upper body and fishy lower body, Seareen can battle both in water and on land, although they are certainly much more mobile in water. It is said that you will know when a Seareen is close by how many Luvdisc and Sweethart there are in the immediate area.

Triton
Water/Fighting
Ability: Serene Grace or Marvel Scale

The masculine males of the Mermaid Pokemon family, Triton are the protectors of the Seareen, as well as other water pokemon, in the sea around Thrinacie Island. It is said that you will know a Triton is close by whenever a Seareen is close by. However, not right next to the Seareen, but off aways, so as to keep an eye on a large area. The distance between a Triton and his Seareen charge matters not to these Knights of the sea, for they are fast swimmers.
As Seareen can, Tritons can battle on land and in water, but again, their advantage is the water.

Both mermaid learnsets have moves found in the Milotic list, with moves unique to the gender. The females can learn such moves as Sing and Charm. The male, being part fighting, parallels Poliwrath, with moves like Vacuum Wave and Submission found in its learnset.