Standish skin dives to rescue a sub in trouble, to a depth of 150 feet. When he returns to the surface, he swims up rapidly. As a professional, expert diver, Standish should know he'd be risking a case of the bends when not decompressing on his way up.
Dr. Standish free dives to 150 ft to rescue the mini-submersible after the collision with the whale disables it. When the SCUBA rescue team arrives, Standish takes 2-3 breaths from the divers regulator and immediately heads to the surface outpacing his exhaled air. If Standish had not taken the breaths from compressed air at depth, this would be no problem as the air would have returned to normal sea level volume, but since he did breathe compressed air at 150 ft. (appx 5 ATM) that air would have expanded to 5 times the volume at the surface. Failure to exhale while surfacing causes the diver to suffer an over pressure of the lungs/thorax resulting in a blowout (pneumothorax) and not the bends which is not a factor at this depth and time on bottom.
When the first sensor is deployed, the escape hatch/sensor room is shown being remotely pressurized to equalize the pressure between exterior and interior so the hatch can be opened, it shows a compressed gas cylinder being crushed due to the pressure differential (improbable but not impossible). Several times during the movie the escape hatch is used to enter and exit the submersible. Yet at no time is is shown the chamber being pressurized, and in fact it shows the scientists immediately opening interior hatches without depressurization or decompression staging.
On the deck of the submarine after swimming in the ocean, Maggie removes her bikini top clearly leaving her back bare. As she puts on the bathrobe we can clearly see the lines of a bra across her back under the bathrobe.