That great homebuilt sub site called psubs.org is at http://www.psubs.org/
that is where you can find a wealth of info on homebuilt subs. I have read the whole site and seen all the pics. It takes a long time to get thru that site. Very enjoyable and educational too. You can learn a lot about what to do and what NOT to do there.
Another site I also especially want you to see Wadester13 is this one that has plans for the sub I'm going to build a modified version of. This one has an open wet cockpit up front and a half dry semi wet ambient atmosphere canopy for the rear cockpit which is the pilot. You can stay a little dryer if you drive. Half dry anyway! Lol. You can also close off the front cockpit with its cover and use the sub as a one man. I selected this design that I will modify to my desires after looking at very many designs. This ambient design does not require a pressure hull. Make sure you check out this one.
Here's the URL http://www.scubatow.com/sub2.html
"The board is green and we have pressure in the boat"