upgrading to new sub?

[duelen]

how do you upgrade to a new sub? whats the requirements?

[Lukemb]

After a few successful patrols you will receive an offer for a new command, then you'll accept and you'll be assigned a new submarine.

[elanaiba]

Of course, it helps if your submarine is not the top of the line ;)

So, for example if you're conning a Gato, you'll have to wait till Balaos become available.