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