The Night Swimmer, by Matt Bondurant

Deeply atmospheric and wonderfully written book. American couple Elly and Fred think they have the chance of a lifetime when Fred wins a small Irish pub in Baltimore, on the southern coast of Cork, but resentment from the locals dooms the pub from the start, while Elly becomes obsessed with long distance ocean swimming, and wants to swim from Clear Cape Island to Fastnet Rock.
The scenes of the ocean swimming were haunting and intense, but the book itself was disturbing and sad. Great writing, and made me spend an hour in a Google-hole last night reading about the area.