I think it's not ideal in the same way that plastics don't belong in an automotive engine bay and concrete doesn't belong" in tension. Add a little bit of fanc

I think it's not ideal in the same way that plastics don't belong in an automotive engine bay and concrete doesn't belong" in tension. Add a little bit of fancy chemistry or some steel and fancy math and they both work fine for cheap. With care and engineering trickery CF in a submersible (compression) probably can work. They still managed to make a few good dives with it despite comically bad decisions in just about every key area. The manufacturing process was primitive, the QC basically nonexistent and procedures didn't make any allocations for the materials (they beat on the thing like it was made of steel). Imagine what a well funded company with experience in CF, robust QC and careful operating procedures could do.