Nope. There's no connection. You have to interact with 3 people before you can go into the underwater cave
1) the ghost girl in cerulean city
2) The green boy above Cerulean City
3) The little boy swimming outside of Bill's Cottage.
1) the ghost girl in cerulean city
2) The green boy above Cerulean City
3) The little boy swimming outside of Bill's Cottage.