Do your maps anchors look like this?
If so then you need to upgrade to 1.4 as the maps anchors look like this ( below ) and the
Slanted anchor is your base. ( Fremantle circled in red in this mission )
When it is no longer your base it will be same as the rest of the anchors. Gotta pay attention to the anchor shapes before you come home.
You must be on the surface to transmit but you can be at "P" depth and receive.