I tried the online mode with a friend, it's funny but it could have been much more improved.

Unfortunatly the game is using the friends code, so you have to connect once to recieve the code before sharing it but once the exchange is done, you can dive with your friend.
Places where you can dive are the one discoverd by the host, that mean you can dive in the abyss even if your guest doesnt have the special equipement, everything else il like the offline mode exept that Catherine is not here. So when your guest is on board, you can move the boat everywhere you can or show him your dolphins tricks.

The big black point is the communication, you only have 16 different sentences including Hello, buy, thanks, yes, no... Of course it's more realistic this way, but it is so frustrating when you want to share your feelings with your guest.. You can use the pen but it's not really easy. A virtual keyboard would have been a big plus. Another thing that could have been improved, you cant share pictures with your guest, that's bad, a system like in MP3 would have been neat.

So it's funny but it's better to have another way to communicate if you want to fully enjoy it.