Per the movie case, this 1961 film revolves around "An American gangster [who] agrees to transport a group of Caribbean island exiles and their national treasury to safe haven, with the intent of eliminating the exiles and keeping the money. Hoping to use the legend of a sea monster as cover for killing off the soldiers the gangster and his crew discover that the legend is true."
Here is a clip - which is about all you need to know about Creature From The Haunted Sea:
Watch at your own risk/enjoyment!
If you liked what you saw in this trailer, you can now watch the entire movie for free through the Internet Archive!