Well, the fantastic Danish hosts of the last intercontinental subsim meeting in Copenhagen/Denmark made it possible for us attending members to actually dive in a privately built submarine, the legendary UC3 Nautilus
http://uc3nautilus.dk/
I remember doing the first dive with Peter Madsen, Neal Stevens and Limkol.
When the hatches got closed, I felt like „omg, i don't want people to read in the news about me tomorrow „tragic indicent: subsim nerds accidently killed themselves in Copenhagen harbour with real submarine (Darwin award)“ or „day 3: rescue team about to make contact with crew of submarine“.
I even called my wife from inside the sub to tell her what I was about to do, and to say good-bye to her, just in case, later I forgot to call her back because I was so excited.
After closing the hatches (manholes), the ballast tanks were flooded with water and so we went down stern first, it was a trim dive, until we hit the harbour ground. There we sat for a while. Thankfully, we had compressed air onboard to blow the ballast tanks to pop up again.
The moment when I realised that the submarine came off the harbour ground and with its 40 tons weight was slowly hovering in the water, was a relief.
The sound and the feeling from the diesel engine running was great, too. The smell of fresh air and the sunshine was even greater.
@Horsa has documented the dives on video. May be, he or somebody else can repost them.
