Welcome to SubSim
If you like SH3 you should try one of the Supermods as Hunter suggests. In my opinion GWX is by far the best. Have a look at the manual to see if you like it
http://files.filefront.com/GWX_MANUA.../fileinfo.html. If you do click on my signature or on the link under it to download the game.
Enjoy your SubSim Experience