Using cheap, commonly available parts for something where (momentary) failure is acceptable is no problem. It might look a little silly, but as you say, that Logitech controller was probably fine. The carbon fibre hull, however, is another story. It was sanded down between layers during construction (which cuts the long fibres and leaves it up to the epoxy to keep it together), and that's not even to mention how carbon fibre is great at stretching forces, not compressive (like what you'd find at the bottom of the sea?). They also put in a window that was rated for like half of the depth they used it at, and bragged about it being acrylic meant that they'd hear when it was about to burst (ignoring the magnitude of the forces at play).

There was a *lot* of things wrong, but the controller was the least of their worries.