I'm writing this story... and I very quickly ran into a small road-block(a small but irritating one.) this story will partially take place underwater, and I was planning on it happening in a submarine, but upon a little research I found that it is a LOT of personnel and submarines are for the US army(from what I've seen) so I was wondering, is there a small submarine-like machine(like that one used in the titanic) that can hold 3-4 people(not for very deep diving).

If anything I can wing it and make my own creation, but I would like to keep the story in the realm of present reality:) If you could give a link to guide me, or even a simple name, I would be eternally grateful.