A really great trailer, that is probably what makes the game great, but after that trailer is gone the rest is just... Offline non workingess that is left.
The game does its own "check" if you have internet connection, if it fails that it doesn't let you go online, but it is flawed.
It doesn't even let you TRY to log in to their servers, nor give any useful information to you to help you troubleshoot the problem.
All it takes to break this system? Exit the game after first launch, then restart it.
So the multiplayer part is out of the window, the UI is very clunky and the functions aren't intuitive to use, basically a lot of saving is done, and those saves you can't use if you are in "Offline mode", so if you built a nice fleet it is all goners.
Overall, this game is now EOL (End Of Life) but the best part about it you can enjoy for free, and that is the launch trailer.
You want naval warfare you have to look at Dangerous Waters or SCS Fleet Command for something that somewhat works, but it is a dead market today with very few good ones popping up to replace the oldies.