There are some terrific titles in the budget MGM Midnite Movies series and this is a good one.
Monster, set in and around the Salton Sea (an accidentally-created man-made salt water lake in California -thank you Wikipaedia), is (for the time) a well-made giant snails movie, is quite convincing and actually made me jump when a monster appeared from a direction I wasn't expecting.
Does 'It' sound familiar to you? An unstoppable monster hides on board a spaceship in the air ducts and sets about killing the crew. No, I didn't think so either. So this alien... Anyway, at 69 minutes it does an efficient entertaining job.
Just one other thing though. Set fifteen years in the future (1973) from when it was filmed (1958), everyone on board the space ship smokes, and the women cook and serve the men their meals, make sandwiches, and pour the coffee, but are allowed to do an autopsy, fix wounds and scream a lot. There is also keep an ample supply of guns on board though I couldn't figure out why unless they were expecting a monster to get on board. And they have artificial gravity which we all know is really to keep the movie's budget down.
No matter, these two black and white movies are good old-fashioned monster fun.