Keeping it to round numbers, pressure at 4000m is about 400atm, or a bit under 6000 PSI. From what I can see, a waterjet cutter ranges from 20,000 PSI to 100,00

Keeping it to round numbers, pressure at 4000m is about 400atm, or a bit under 6000 PSI. From what I can see, a waterjet cutter ranges from 20,000 PSI to 100,000, depending on model and which source you trust. So if they could contain it to a pinhole, they'd probably be lucky enough that the incoming stream wouldn't cut through the far side, though the same isn't true of the occupants. Though as you said, the far more likely outcome is that the vessel would crush almost instantly.