Every other month, on one blustery Saturday evening or another, a boisterous chorus arises from the shores of Drakes Beach. Some of the singers sound choir-worthy, and some sound awful. But tone deaf or pitch-perfect, they are all having a good time, because not even the grumpiest of curmudgeons could have a bad time singing a sea shanty.

“You don’t need to be an expert singer or even know the lyrics,” said Fiona O’Kelly, the…