>>23277523In order to get there you need to either be traded a Pokemon that knows Cut so as to skip the SS Anne entirely, or let yourself be defeated in a battle on the ship after receiving the HM. Once you get a Pokemon with Surf, you can swim off the right side of the dock leading to the ship to reach an area with a truck that does nothing besides fuel rumours, and a hidden Lava Cookie to the south.
It was in R/B/Y too, sans cookie.
