Have you seen the video on Differential Pressure or as it’s commonly known (maybe?) as Delta P? I saw this video a week ago and its apparently the cause of quite a few commercial scuba diving accidents. If you’ve got the time check out the video:
It seems pretty sad that commercial divers don’t understand how pressure works and when your at the intersection of two bodies of water. Actually the saddest part of this video is the part where the diver asks if the flood gate is closed, the worker says yes, the diver goes ahead with the work and is sucked through the flood gate.
The moral of the story is if you are working on clearing an area between two bodies of water, they are likely to have two different pressures and once that blockage is cleared the pressure difference is going to re-balance. If you are in the way, you could die.