Question about the conning tower

[sillysunday51]

I notice that when i go to para-scope depth this antenna like thing goes up then when I surface it goes down. what is it and what is it's function? I tried to look it up but I have no clue what it is called.

[markdenny]

Its the subs radio antenna

[sillysunday51]

That what i kinda thought is it suppose to extend under water and retract when the boat goes top side, wondering