It is impossible to survive underwater explosion in such a cramped space. Enormous pressure would smash everybody and everything.
Gold is very heavy. When Nairobi takes the two gold ingots as if they were earrings she handles them as two hollow plastic ones. Those two gold ingots would have a mass of 12,5 kg (27,6 lbs) each circa.
The robbers handle gold bars as if they were made of styrofoam. Gold is almost twice as heavy as lead.