Beat team aqua at their hideout in lilycove. Then you can surf there. if there is 2 guards blocking, talk to them and they will say where their boss went. Then go to slateport city and go to the crowd.
MOSSDEEP CITY
in the city mossdeep
Mossdeep City.
Mossdeep City
You have to surf from LILYCOVE city to the right
Mossdeep City
In Pokemon Ruby/Sapphire/Emerald in Mossdeep City.
Steven gives it to you in his home in mossdeep city.
You can buy these at the mossdeep city pokemart.
North of Mossdeep City! Cha Cha!
Steven gives it to you at his house in mossdeep city.
You go to Steven's house in Mossdeep City