I really don't think that Skyrim is going to have much to do with the oceans - the setting is in the mountains.
It might be cool at some point to implement ship mechanics into the game, but I don't think we will see it this time.
Skyrim is set in Skyrim, a diverse environment that not only includes mountains, but tundras, rivers and lakes, and a coastline to the north.
I feel like people are starting to confuse the Nords with real life Vikings... is this still TES?
Longboats exist in TES, I don't see any reason why the Nords wouldn't use them. The structures, the armor, and culture in general are all based heavily on the Vikings. I am positive we will see longboats.
I think it would be great to be able to use them, in realtime. I'm not really all that interested in having a battle at sea, but being able to sail up the rivers and along the coast would be a very cool experience.