Lets see, we'll make an assumption of a normal treatment depth of 60 fsw. Thats almost 66 feet or 3 atmospheres absolute. (Note- if anyone feels like running the real numbers knock yourself out- this is just a rough approximation
) Thats a bit less than 30 PSI more on the inside of the door than on the outside.
I'll use Catalina as an example since I work there- the door is held shut by the interior pressure when the chamber is at depth. (Chamber doors open inward) Door is (very) roughly 5' x 3', or 15 square feet. That works out to 2,160 square inches. If we multiply by the 30 PSI that would get us 64,800 pounds of pressure holding that door shut. (It's a steel door and probably a couple of inches thick)
Offhand I'd say we can call BS on that one.