you get sent to the moon to capture a virus which is deoxys
by surfing!
in mosdeep
After you defeat the mosdeep city gym and the team aqua (also in mosdeep city but only after you finished the gym) you can get dive from the guy in the house in the south-west of mosdeep
mosdeep gym or from gardevoir
Mosdeep City Surf there from Lilycove
Surf east of lilycove city.
After beating Mosdeep City Gym.
Mosdeep in emerald, Sapphire and ruby
Tate & Liza in Mosdeep. Psychic type.
He is a little bit to the west of mosdeep
go to mosdeep city talk to the professor and he will take you to moon
go to Stevens house at mosdeep city i think it was?