I started cleaning up this scrap piece of delrin or uhmw (don't know which).  Just ordered a end mill holder for 3/8" bits. I will be happy if I get a perfect rectangular piece as this is the first real machining I have done.  The hard part is going to be the o-ring grooves, I think that there should be a gland and a face seal.  If I get it right it should be water tight to 800+ fsw (~356psi), I am just hoping there is space for everything I want to put in it.

I don't think that there can be much found on the internet about making a submersible 1atm box, it is probably mostly guess and test with the big companies.  I won't make 3d drawings, but I will put cad drawings in the repository after I get the box made and can get measurements.