Did you edit your DangerousWaters.ini to select the connection you wanted? That's how you force it to use a connection.
I sometimes had an issue getting DW to connect and I found that for me, DW listed two adaptors with the same name in my adaptors file. Also, It wouldn't connect for me as long as I had Hamachi running. All I did was shut down all the adapters except for one and it used that and connected fine.
Dangerous Waters IS fun with multiplayer, but you have to have an attention span and be prepared for a long game. It can be VERY rewarding with multiplayer. This game also does NOT like lag. It tends to crash on me if I have a laggy connection.
Also, for your enjoyment, here's the known issues so you can work around them when designing (or playing) scenarios. The DSRV is broken. It's steerable fine, You can use it to deploy your special forces. But whatever you do, don't order it to dock to your sub. It will just crash into it. It's docking abilites are completely FUBAR'd.
Aircraft also tend to like to fly until they run out of fuel and then crash. They have no instict that they've hit "Bingo Fuel" and need to turn back to land. If you set up scenarios, just keep these points in mind and you can make some fantastic missions. Also, check out the downloads section here and also look at
http://www.subguru.com/
There's some great scenarios there as well as the excellent "Red Storm Rising" campaign.