HI,This is Pravin.
After you beat the 7th gym leader in mosdeep city go to to the space building with the rocket behind it.A team magma grunt will be covering a door. defeat him and go upstairs.
there you will find Steven with team magma admin and leader. you team up with Steven and defeat them. Then talk to Steven and he will take you to his house.Then he will give you DIVE!
Make sure the 3 Pokemon that you pick are level 40 or more,otherwise you'll make it hard for steven.I used a
LV.40 swampert
LV.40 Armaldo
LV.40 Wailord
I also had a LV.40 Exploud but I didn't use him.
Hope I helped.
Chat with our AI personalities
get a hm called dive attach it to a water type pokemon and go on water and use dive.
You go to the Rustbord Pokemart :) hope that helped
go to Stevens house at mosdeep city i think it was?
If you use dive in dark patches of water then go in the seaweed then you can catch chinchou.
you just press b and you will go up =P