Where to Find and Catch Wailord
From Pokemon Go Wiki
Wailord are found and captured in Nest and Habitat locations.
Nests
Wailord Nests are locations that consistently spawn Wailord.
Habitats
Wailord Habitats are spawn locations where Wailord 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: