Top of Conning tower
 

Guys in SH IV there are some references to a top level iside the conning tower specificaly in requard to drive dept can someone explain to me what key do I hit to reach the tower (inside) and where do I find the depth gauge sorry for newbie question thanks

For me to get to the Con, I use F9. If you hit F1, it should give you a list of all hotkeys.

The depth gauge on your screen is bottom right, you can click the tab underneath it to access greater depth settings. As for gauges inside of your sub, mods may change it, some have workable dials you can click and set depth up to 600 ft.