I own my big continent, finished nearly the tech tree, have started to build my space station, but I haven't found an efficient way to control enemies ship movement near my borders (or anywhere) I don' want to build tons of ships as I already have the biggest fleet by far. However, a big continent has a long border and often I can't stop the enemy transports on the sea. They don't do many harm, but I am afraid that in higher levels when I am not technological ahead it is vital to block enemy transports and sink as much as possible of them on sea. I would like to have something like the sonar system of CTP2 to detect ship movement that my air force can react or even I can move my fleet in time. I have seen the radar tower for the expansion set. This might help, but I am not sure if this works for sea as well. How do you control your coasts?