Simply use dive or an escape rope.
its in Marine Cave
In Pokemon Emerald, Groundon and Kyogre are legendary Pokemon. You can find them in the Marine Cave and the Terra Cave.
Marine Cave
Kyogre is the name of a Pokemon only available in the Pokemon Sapphire and Pokemon Emerald video games. Kyogre can be found in the Cave of Origin, near Sootopolis City, in Sapphire, and it appears in the Marine Cave in Emerald. The location of the Marine Cave changes periodically in the game.
Desert ruins, Ancient tomb, Island cave, Sky pillar, Cave of origin, Marine cave, Terra cave.
I do not know if you can catch Kyogre in Emerald but if you could, Kyogre will be in the Cave of Orgin at Sootopolis City. ;) ANSWER At marine cave, but I dont know how to get there
Kyogre is in marine cave. (Beat the elite 4 first then talk to the professor in weather institute to know where Marine cave is)
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.
Answer 1: you cant only by tradeing or hacking stupids Answer2 : You can get Kyogre at Pokemon Sapphire (Cave of Origin) , Pokemon Emerald (Marine Cave) , and Pokemon HeartGold (Hidden Tower).
In the cave of origin and marine cave.
Kyorge does not appear in Shoal Cave. In Pokemon Sapphire Kyogre appears in the Cave of Origins as part of the story. In Pokemon Emerald Kyogre appears in the Marine Cave after defeating the Elite Four.
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.