Sneak Peak II: The Sea Forts
http://www.subsim.com/radioroom/showthread.php?t=117511
Those Forts were built to protect the English Coast from uboats and surface vessels and some still stand today.
They are land units but can be torpedoed and according the Kpt Lehmann are quite deadly
New German coastal ship
Additional Information:
Including whales was discussed but tabled:
But there's hope yet:
http://www.subsim.com/radioroom/showthread.php?t=123111
http://www.subsim.com/radioroom/showthread.php?t=123199