Haunted Harbor (1944) is a Republic serial, based on the novel by Ewart Adamson.

Plot
Sea captain Jim Marsden is about to be hanged for a murder he didn’t commit, and is rescued from the gallows by two of his crewmen. To clear the captain’s name, they head for the island of Pulinan, where they believe the real murderer is hiding. During the search for the killer, one thing leads to another and Jim and the crew soon find that their troubles have just started. Investigating a possible hiding place of the killer, Jim encounters huge sea monsters in Haunted Harbor.

Cast
Kane Richmond as Jim Marsden
Kay Aldridge as Patricia Harding
Roy Barcroft as Carter (AKA Kane)
Clancy Cooper as Yank
Marshall J. Reed as Tommy
Oscar O’Shea as John Galbraith
Forrest Taylor as Dr Oliver Harding
Hal Taliaferro as Lawson