sea cavern but first you have to beat the elite 4 and talk to the guy in the weather institute
You can not see kyogre in emerald
You cannot see Kyogre in Pokemon Ruby because it's a version exclusive to Sapphire and can be found in Emerald also.
I remember it is in a cave, where you rescue Kyogre. If you use flash, on the way to rescuing Kyogre, you will be able to see the HM lying on the ground in the same room as Kyogre.
Kyogre can be found in the Cave of Origins in Sapphire and the Marine Cave in Emerald.
after you see groudon and kyogre fighting in the lake, surf to the other side and talk to wally. he will take you there and let you in.
He goes to sootopolis city...once you get to sootopolis you will see a video showing rayquaza ordering groudon and kyogre to stop their fight...then he returns back to SKY PILLAR.
its at seafloor where you wake up kyogre if u go in that place where its fogy if u go in you will see a pokeball click it and its gonna be earthquake
In only emerald you can see them fight the second you enter sootoplos the place that has the eighth in in emerald
(After beating League)Go to route 104 and surf forward.There you will see a diving patch.Dive and you will see a cave,go in it.You will see the Legendary Kyogre.(Can be catched with Pokeball)
You must have dive. Dive from Mossdeep City and enter the cave to your lower left. Dive right back up and you will see Groudon and Kyogre fighting.
You go to Sootopolis City. There you will see Groudon and Kyogre fighting, and Rayquaza goes to stop them. Then he goes back to the Sky Pillar.
the answer is: in dewford city cave, the first guy you see.