This is a fantastic looking boat that is controlled by a NXT. From what I can tell from the Brickshelf photos, steering is done with a NXT motor and the dual props are controlled by the NXT via some PowerFunctions motors.
I love the pneumatic tubing that gives the boat some shape. The boat is controlled by a mobile phone via Bluetooth.
More (italian) info here - hobbymedia.it/24101/lego-nxt-rc-boat-barca-radiocomandata-con-mindstorms-nxt