Objects passing from air to water without leaking

[Boy@n]

Is there a system (e.g. valve) which enables objects (e.g. ball) passing from air to water containers without leaking?

I imagine this is near to impossible since water is nearly 1,000 times denser than air...

To make it work air would have to be compressed so air density in air container is close to that of water density in water container?

I wonder how those openings in submarines work (serving divers to go in/out of water at depths) where water doesn't fill the submarine?
(I doubt air pressure in submarine is equal to water pressure there at great depths, or is it?)

[Daever]

Is there a system (e.g. valve) which enables objects (e.g. ball) passing from air to water containers without leaking?

Yes there is a very special valve that governs just this, in engineering terms it's referred to as the Atmosphere.

I imagine this is near to impossible since water is nearly 1,000 times denser than air...

Not true, conduct an experiment: turn on a bath, step into the water, then step out, neglecting the water on your legs and assuming you have a plug in, observe if it leaks. write back with the results, I'm interested to know what they are.

I wonder how those openings in submarines work (serving divers to go in/out of water at depths) where water doesn't fill the submarine?
(I doubt air pressure in submarine is equal to water pressure there at great depths, or is it?)

some special kind of submarines do run the same internal pressure as the outside water pressure, kind of like upside-down boats. The titanic was a great example of this.

[Boy@n]

I see my question is not clear enough.

I'm asking about a way for object to pass into water from air through vertical 'wall' (say via valve in middle of that wall)...

[MATLABdude]

An airlock?
http://en.wikipedia.org/wiki/Airlock

[Boy@n]

An airlock? http://en.wikipedia.org/wiki/Airlock
Thanks! That's pretty close to what I'm seeking...

Airlock: 'The air pressure of the airlock—the space between the doors—is equalized with that of the environment beyond the next door to open.'

Is there a simpler way to make small objects pass from air to water (without the need for adapting pressure)?