Looking for information on the internet for guidance on how to build a
submarine for a middle school chemistry project.

Here's a guide to building a submarine for a science project though
I'm not sure how much submarines have to do with chemistry.

http://www.missouri.edu/~wwwepic/Pictures/submarine.jpg

Toy submarines often exploit a chemical reaction between baking powder
& water to generate a pocket of gas beneath the sub, increasing its
bouyancy and causing it to rise. That's where the chemistry comes in.

   Here's one page from a Google search using the terms "baking powder submarine":

http://www.torgo.org/bpsubs/

And of course there are lots of other pages that pop up as well.

http://www.falconrobotics.org/rovweb/rovworld.htm

Not sure that a sub is chemistry but the article is interesting.