Abstract: A watercraft has a buoyancy hull with an upwardly bode rail forming an arcuate guide for a passenger stand which allows the passenger to remain substantially upright as the buoyancy hull rolls beneath the stand. The stand can have rollers riding on the rail.

Abstract: A piece of furniture has a frame and a part capable of rocking on the frame at a natural rocking frequency. A drive has a sensor for detecting movement of the part on the frame, a drive motor connected between the frame and the part for rocking the part on the frame, and a controller connected between the drive and sensor for rocking the part on the frame at the natural rocking frequency up to a predetermined maximum angular displacement of the part on the frame. The sensor detects angular movement, that is angular speed, angular position, and/or angular acceleration of the part on the frame. The controller has a response field and operates the drive in accordance therewith.

Abstract: A watercraft in which a beam having a seat for the user is supported by two stanchions pivotally connected to a support frame below the beam. A float elongated in the direction of travel of the watercraft is provided on an upper part of the frame below the beam while a ballast is provided on a lower part of the frame below the float. Between the float and the ballast, lateral arms of the support frame extend for engagement by the legs of the operator who can thereby swing the float and ballast assembly in a balancing operation during travel of the watercraft.