Floating Wire Antenna
 

How does it work? What are the required parameters for it to function?

I cannot seem to make it work when underwater. I normally ensure I've extended enough wire and I never seem to get it to work.

Welcome aboard!
 

Who knew 450 hours later I'd still be playing a 15 year old Submarine game.

The wire antenna is a passive receiver that just floats on the water. If there is a message, you will get it. If you are going to fast it may not reach the surface.

The mission may not have messages or the messages may be much later.
Test it on a quick mission, it's a got a message right at the beginning.
Check the 3D view and make sure the radio wire reaches the surface.