Or a selkie Romance set around WWI where the selkie is male and the heroine has lost her husband in the war and is getting by doing his job. There was such a lot of genderfuck during WWI. Women taking men's jobs, men experiencing the "female" psychological malady of "hysteria," men considered no longer living up to "manliness" because of injuries, the betrayal of the patriarchy.

Oh for world enough and time!