The Sea Bat (1930)

The West Indies island of Portuga exists mainly for sponge diving. But the best area of collection is frequented by a very large manta ray. Nina loses her brother to the creature and is comforted by a newly arrived minister, who seems very interested in an old poster offering a reward for a convict recently escaped from nearby Devil's Island. More deaths attributed to the sea bat follow before Nina resolves her feelings for her comforter.