Welcome to the group.
May I suggest something? A way around your dilemma may be to have someone with a finished design share their ideas with you. Building a sub really is simple as long as you pay attention. It's basically a no-brainer. But, there are many details to be sure of.
Depending on your preferences, a wet canoe-type with simple "wind"shield would probably be a thrill and a half. (please, if you build/use a wet sub, get your SCUBA certification). Closed deck like a kayak. Simple ballast system, simple tankage. Simple propulsion. Simple controls. Built in a few weekends if you've done your homework and have simple plans to work from. You could, if you were adventurous, do it from your head. That's if you are a visual person!!!
In any case, hang around for lots of opinions and good, sound information.
Rick
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Rick Lucertini
empiricus@sprint.ca
(Vancouver, Canada)
"Most people die with their dreams still inside them."