Maybe one based in the chilean dolphin or
tonina as it's called here, which is the one in the pic bellow. As in typing it may not look like it, but I would give it Water/Fairy since there's a mythological creature in chilean culture called Cahuelche that is said to look similar than said dolphin.
As for stats I would put it in the somewhat tanky side, kinda similar to Milotic but with more defense and hp and less sp.def. Also waaaaay slower. No evolution.
HP: 110
Atk: 75
Def: 85
SpAtk: 75
SpDef: 100
Speed: 55
BST:500
Not really sure about its overall design or name, but it's shiny can be a pastel pink, in reference to the pink dolphin from many southamerican rivers that is actually often refered to as
tonina as well.
There's also the common dolphin that is well... common! You can even find those in Greece. And speaking about Greece there's a legend that talks about how a crew of pirates were transformed into dolphins after attempting to kidnap Dionysus.
Also seeing the white-ish coloration in some parts the dolphin in the picture above, it can maybe evolve into a killer whale that isn't actually a whale cut a big ass dolphin, and given the pirate legend and awful name the orca has it can have the Water/Dark or Water/Fighting typing.
Stats for both would go more in the speedy side for common dolphin and more on the physical side for orca
Dolphin:
HP: 70
Atk: 75
Def: 60
SpAtk: 50
SpDef: 60
Speed: 115
BST: 430
Orca:
HP: 90
Atk: 110
Def: 100
SpAtk: 65
SpDef: 60
Speed: 75
BST: 500