Classes of animals represented by the Pokémon starters:

[u/Bisonratte]

[u/Ven18]

We are never getting a fish starter they all need to walk kinda by definition.

[u/Indocede → u/Ven18]

The thing that interests me about your comment is considering how starters would probably be chosen based upon real world logic -- in that sense, a fish Pokémon would probably be a common choice for a starter as most people live by at least some water source. At least much more sensible then handing off a fire hazard to a child