When Nathan calls in an evacuation of Founder's Square, Laverne okays it without hesitation. However when he tried to call for an evacuation back when his dad was still the chief of police, Laverne told him that only the chief can authorize such an evacuation, making Dwight the only one who has the authority to do it now.
The diving suits used do not protect the users from deep sea pressure as discussed. The user still experiences the full pressure on the suit and would still have to depressurize. A hard suit is the only kind that the diver operates in normal pressure, but is far too heavy to use out of the water.
Vince and Dave are caught in the edge of the "crush" pressure and experience the "bends". The bends only occur if the person has been subjected to high pressure for a period of at least 20-30 minutes. Short exposures of less than 10 minutes would not cause major/life threatening problems.
The high pressure causes basketballs, plastic ice chests, buoys and other objects to collapse, breaks car windows and kills people, yet the tires on all the cars remain inflated. Car tires carry about 35 PSI inside while the "crush" pressure is well over 300 PSI so the tires should be squashed.