lol mate - seriously read some of those links that were posted though. But it wasn't registered in the US & it had no maritime industry classification.
Your boat or your friend's catamaran passenger vehicle are different to a submersible that will never sail in and out of ports. Most regulations regarding submersibles are based on local rules. This was a submersible carried out to international waters from a Canadian vessel.
They weren't in any violation of any regulation, they were just in a weird grey area. The links above that @nudge posted explain it better than I can, so to satisfy your curiosity and get some answers to your questions I think you should check them out.