Where to Find and Catch Kyogre
From Pokemon Go Wiki
Kyogre are found and captured in Nest and Habitat locations.
Nests
Kyogre Nests are locations that consistently spawn Kyogre.
Habitats
Kyogre Habitats are spawn locations where Kyogre is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: