I am trying to remember a sci-fi horror picture that has a quasi (as I remember it) connection to "Creature from the black lagoon".
The major part that I remember is that scuba divers find a submerged UFO. While exploring it, they open a door to a room with some type of machine in it. After activating it, accidentally, the machine pushes out a cylinder the size of a large soup can encased in ice.
I believe that the scuba divers not wanting to do anything else, leave the room and swim back to their base. The block of ice melts and exposes the metal can inside. Somehow the metal can opens up and what comes out is a "creature from the black lagoon" type "gill-man".
Additional information is that it seems that the movie may be a quasi-precursor to "Creature from the Black Lagoon" because it points out things about the birth of the creature that is not in the movie but can be found on wiki.