I like Terramar a lot – his episode was an oddball, but I couldn’t pass up being him if it meant having a necklace from something literally called the Pearl of Transformation. I think in his swimmy form he would be considered a merpony. I’ll leave it up to individual posters to decide if merponies ≠ seaponies ≠ hippogriffs in aquatic morphs, but they’re basically the same in my mind. Hope you like the art!