The inspiration for the novel came when Wells caught a glimpse of May Nisbet, the daughter of The Times drama critic, in a bathing suit during her visit to Sandgate.

Feigning a desire to become part of genteel society under the alias "Miss Doris Thalassia Waters," the mermaid's true intention is to seduce Harry Chatteris, a man she saw "some years ago" in "the South Seas—near Tonga" and who has since captivated her.

As a supernatural being, she is indifferent to the fact that Chatteris is engaged to the socially ambitious Miss Adeline Glendower and is attempting to redeem his misspent youth by entering politics.

Couched in the language of fantasy and romance, blending with light-hearted social satire, The Sea Lady explores serious themes of nature, sex, the imagination, and the ideal in an Edwardian world where moral restraints are loosening.

[6] Her seaside reading material includes Sir George Tressady,[7] and she is compared to the eponymous heroine of Marcella,[8] both novels by Mary Augusta Ward.