"The Horror at Martin's Beach" is a short story by H. P. Lovecraft

H. P. Lovecraft

Howard Phillips Lovecraft --often credited as H.P. Lovecraft — was an American author of horror, fantasy and science fiction, especially the subgenre known as weird fiction....

 and Sonia H. Greene

Sonia Greene

Sonia Haft Greene Lovecraft Davis was a one-time pulp fiction writer and amateur publisher, a single mother, business woman and successful milliner who bankrolled several fanzines in the early twentieth century...

 (1883-1972). Also known as "The Invisible Monster", it was written in June 1922 and first published in November 1923 in Weird Tales

Weird Tales

Weird Tales is an American fantasy and horror fiction pulp magazine first published in March 1923. It ceased its original run in September 1954, after 279 issues, but has since been revived. The magazine was set up in Chicago by J. C. Henneberger, an ex-journalist with a taste for the macabre....

(Vol. 2, No. 4, 75-76, 83).

Synopsis

Sailors kill a 50 foot creature at sea after a lengthy battle. The creature bears strange anatomical irregularities such as rudimentary forelegs and six-toed feet in place of pectoral fins and single large eye. After inspection by marine biologists, it is revealed to be just a juvenile. The captain who captured the creature tours the coast and profits from the corpse of the deceased creature. As the captain attempts to finish his business at Martin's Beach, a group of swimmers are attacked. The captain and others attempt to rescue the victims but it is too late. The good samaritans and the captain are hypnotized and pulled into the water by the creature's mother to the horror of an onlooking crowd.