Hi, It may not be the best title chosen but here is the question. If I have one container that has two compartments, one has a battery pack built from several alkaline cells and the second compartment has some pcb, wiring etc. The two compartments are separated each other with a plug, no communication port between the two. My container is supposed to be waterproof. If I drop this container in the water at 30m depth and water enters in the battery compartment, do I expect to have pressure built up in the unit when brought to the surface ? When the container is opened up, is there a safety hazard because of this possible pressure building in the unit ? There should be no chemical reaction between alkaline batteries and salt water that builds up gases ( I think). Thanks for help.