You just have to surf to the right of Lilycove city. If you can't because wailord is in the way, you probably need to go to mt. Pyre. If you've already done that, then probably go Slateport and go to the place where the ships are. There should be a big croud outside the it. If nobody's there, don't bother going inside....
You have to cross the water. There are two things to do before that. YOu have to beat your rival at the MegaMart in Lilycove and to beat the Team Aqua from their base at the shore of Lilycove.
Head to lilycove city then surf east to mossdeep city go into the gym and defeat the leaders for badge #7. Finally one more to go, go into steven's house which is in mossdeep city talk to him to get the HM Dive use it to reach sootopolis city this is where the last gym is!
You explore the dive spots and find sootopolis city and seafloor cavern.
Mossdeep City is in Ruby, Sapphire, and Emerald.
Mossdeep cityit is in mossdeep
Mossdeep is in Hoenn not Sinnoh
After beating tate and liza head to steven's house in mossdeep city he will give you the HM Dive.
To Steven's house in Mossdeep City.
You have to beat the gym leader first... then you'll find them there.
After beating the E4, go to Steven's house in Mossdeep City and a Pokeball is on the table in the house. Take it. Inside will be Beldum.
you have to
mossdeep city dhoom
The Gyms are Roxanne in Rustboro City, Brawly in Dewford City, Wattson in Mauville City, Flannery in Lavaridge City, Norman in Petalburg City, Winona in Fortree City, the twins Liza and Tate in Mossdeep City, and Wallace in Sootopolis City.
You have to get the HM move dive and sail over to Mossdeep or Sootopolis from either Lilycove city or Slateport.
You have to surf there first. From Lilycove City, you surf to the right till you reach Mossdeep City.
You have to surf from LILYCOVE city to the right
Surf east from lilycove city.
in mossdeep city
in mossdeep city
in the city mossdeep