Beneath the Rio Cobre by W. H. Vigo

In 1920s Jamaica, solicitor Archibald Grant is hired as a mediator to accompany wealthy Englishman Mr. Chambers on a hunting expedition, as he pursues a rare, unnamed creature living nearby the Rio Cobre river.

Archibald finds the local community in turmoil. A series of mysterious drownings have recently taken place, rousing accusations of murder and witchcraft among the countryfolk. As Chambers hunts and the community cowers, Archibald discovers a sinister truth baring its teeth from the Rio's murky waters.