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