Pokémon Mystery Dungeon: Blue Rescue Team and Red Rescue Team/Stormy Sea

To enter Stormy Sea you have to beat Rayquaza. After beating Rayquaza talk to Medicham then Lombre then go to Whiscash’s pond and he'll give you the TM dive.

Boss Battle: Kyogre
Kyogre is on 40f. You cannot recruit him on the first try. On the second try make sure your size is not over 2. Then go challenge him and he might join. He has a 50% chance of recruiting him.