Pressure on an item underwater

The pressure exerted by a liquid increases linearly with depth, i.e. the deeper you go the more pressure is exerted. However, this pressure is exerted uniformly at a certain 'level' in all directions. Therefore, there is a greater force (note force not pressure) pushing a submerged object upwards than downwards; i.e. there is a net force upwards. This is buoyancy.

 

With a little thought and be reading what I have posted above, you should be able to answer this question yourself.

 

I'm confused. Are you pumping air down? "pump air too, say a depth of eight feet"
Or are you pumping the air up? "escape its chamber?", "get the low pressure air out by pointing it upwards or down, (at that eight foot level)."

 

Well, unless your container at the 8 foot level is both rigid in structure and held securely in place, the air down there will happily come up from that depth without any help from you... Your container will implode, or it will rocket to the surface.

OTOH, if it is both those things, then you move air to and fro with free abandon. You could blow in it if you chose.


Look, it seems tome you're beating around the bush. I think you're going to need to illustrate what you are talking about if you want meaningful answers.