I'm not talking out of my ass here; Eastern dragons and fishes are closely related beyond the only myth the fandom knows about the carp turning into a ryu because of Pokémon, to the point ancient thesaurus put them together in the same category of Ryougo.
I mean, dragons have been consistently put in an aquatic context in this very story since day one, whether it's the dragons in Arabasta's bathroom, the Ryugu Kingdom, Luffy comparing Momonosuke to an eel (so to a fish, not a snake) or now Seiryu being a model of the Fish-Fish family. Heck, Oda's own bathroom is ryu-themed; just imagine how aquatic he finds dragons.
Again, I don't know what's so weird about a creature with carp scales, lobster eyes and catfish whiskers that primarily has an aquatic symbolism (as per experts like Chevalier), is put in the "Dragons and fishes" category in ancient thesaurus and has been visually compared to a fish instead of a reptile in One Piece being included in the "fish" family.
is the head of the fish clan in Chinese mythology and