A swimming platform assembly that is adapted to be mounted to a drive assembly housing of a watercraft includes a support platform adapted to provide a stable support for a swimmer and a mounting assembly coupled to the support platform to mount the support platform onto the watercraft. The support platform has planar top and bottom surfaces, while the mounting assembly is secured to an intermediate portion of a drive assembly housing of the watercraft such that the top surface of the support platform is disposed below the surface of the water when the watercraft is stationary or is traveling in a forward direction at or below a critical rate of speed, and such that the bottom surface of the support platform is disposed above the surface of the water when the watercraft is traveling in a forward direction above the critical rate of speed.