U use surf then rock climb and kyogre should be there
go far left on dewford island and the surf up as far as u can
There isn't a third island in Pokemon emerald.
when your in the cave where you get ditto (in fossil manics house) go in the cave after you beat the elite 4 then go all the way right
after you beat the Pokemon league go where the shoal cave is then look to your left and the is a dive spot dive and go through and then go up then there is a cave and that is the marine cave.
go to the cave of origin in sootopolis
Sootopolis city but you cannot go in.
Go east of rustboro city.
You go to birth island
Zubat is all I know. Go there yourself and find out!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
It's really simple: You just go in the middle of the cave.
You get it at marine cave. Go to mount pyre then go to sotoplois city. (where the eight gym is) Go to the cave there.
go to route 127 and 128,then go underwater.