The answer to what it is made out of was lurking at the bottom of the page:

Deep Flight II (DFII), which has been designed and is awaiting funding, will be built with acrylic crew hulls for 3,000 feet or with titanium hulls with conventional viewports for 20,000 feet. Hawkes has recently resolved all engineering design issues for Deep Flight II and is actively pushing this program forward. To do so, H.O.T. is looking for corporate sponsors and individual patrons

The craft design seems thin to support 20,000 feet. The glass which seems like the weak spot is really Scotty's formula for "transparent titanium"

SDAI-Tech1