Instructions
Travel to the Weather Institute, located along Route 119. It lies west of Route 118 and west of Fortree City. Speak to the professor inside the Weather Institute. Players will eventually learn that Kyogre dwells in the Marine Cave, which may appear along Route 105, 125, 127 or 129. Players should move quickly to that location, as the Marine Cave may move if players take too long.
Move to the Marine Cave's location. Players may choose to use a Pokemon's "Fly" ability to hasten the trip. Route 105 lies south of Route 104 in the Hoenn region. Route 125 lies north of Mossdeep City and Route 127 lies south of Mossdeep City. Players can find Route 129 south of Route 128.
Use a Pokemon's "Surf" ability to navigate the waters of these Routes. Move until you encounter a dark patch of water. Rest on that spot to get teleported into the Marine Cave. Advance into the second room of the Marine Cave and approach Kyogre. Weaken it in battle and use a Pokeball to capture it. Take it to a Pokemon Center after capture for healing.