Manda’s serpentine lóng/chinese dragon body isn’t very impressive when his co-stars are Godzilla, Anguirus, Ghidorah, and the rest. Compared to them, he’s a generic sea serpent. But he’s not without charm.
Tanytropheus is a good fit. Aquatic, serpentine, predatory, charming, etc. Also, I like the idea that no one knew that he wasn’t a sea serpent until one time when he walks onto land.