Well the "glue" in this case is actually a very good material for the application. Epoxy has compressive strength comparable to structural steel, and more impor

Well the "glue" in this case is actually a very good material for the application. Epoxy has compressive strength comparable to structural steel, and more importantly its density is almost the same as water. This means you can make incredibly thick walls for a small internal volume while remaining buoyant. It also resists biofouling and corrosion, which is why it's popular in other marine applications. Submarines of this size should be using composites, once sufficient data is gathered on their behavior to develop proper factors of safety. The issue was all the idiocy that came after. This team was going to kill people no matter no matter what they made the sub out of.