In the latest “Road to Battlefield 4” blog post, the Battlefield devs discuss how Commander Mode was created for Battlefield 2 and how the idea evolved to what it has become in Battlefield 4. Within the blog post is an animated gif of some Commander Mode concept mock-ups for Battlefield 4. The primary images of this gif are the familiar top-down view of Siege of Shanghai.
However, if one is to break the gif down to its individual frames for more careful viewing, we can see what appears to be a new map. On the right side of this new map appears to be a dam. They have already discussed a levee that can be breached to flood an urban map, so whether or not this dam will do the same we will have to wait to see. It seems fairly clear to me this is not the same map, however, because the levee map shown in the Levolution trailer was more of an urban environment with tight streets and many more buildings than this map shows.
Keep in mind that the images in this gif are apparently meant to illustrate the evolution of the Commander Mode concept for BF4. I would assume that any map images this detailed used for these concept images is likely from a real map created for the game. However, much about the commander UI, assets, and other things seen in these images is certainly subject to change, so this certainly isn’t confirmation of a submarine in the game, although it is confirmation they have considered it.