Minecraft wiki entry for Miscellaneous, associated text: When placed on the sand, the boat overlaps the pressure plate, powering the block below, which should activate the piston by quasi-connectivity. When the piston is updated, it pushes the sand and boat up, unpowering the plate and block, deactivating the piston again. By the time the boat lands on the pressure plate, the piston has stopped checking for activations, resetting the circuit.