Caves can run underwater genius, and Sinnoh is literally known for having a complex cave system underground.
Is it really such an impossible idea to think that in the world of Pokémon, there couldn't be cave systems underground that connect regions?
I mean shit, how do you think Steelix naturally showed up in places like Route 45 in Johto, or the Wilds of Galar? We were under the impression that they were only evolving naturally at Iron Island, for obvious reasons.
