It's all fairly basic. If there's enough pressure discrepancy, a pumpkin that reached a certain depth would implode. The question (after you've figured out how to make a pumpkin sink at all) is ...

The pressure at sea level is about 14.7 pounds per square inch, which you can't feel, according to the National Ocean Service, ... At that depth, the pressure is about 470 pounds per square inch.

Pressure regressions are recognized on P-D plots when the magnitude of overpressure reduces with depth and can be illustrated on an overpressure-depth plot (Fig. 9). Click here to enlarge image ...