The invention relates to a variable-height platform, which is fitted to a watercraft and has an additional travel and/or a longitudinally movable mounting plate, by positive control such that obstructions in the pivoting area can be fully bypassed without long pivoting arms and special linear-movement cylinders, and a reasonable immersion depth of the platform is ensured in all cases and, in the event of failure of the linear-movement cylinder, the platform can always be moved to the position A by an energy store or accumulator.