Abstract: The invention comprises a mobile frame and a floatation frame having a tractor pivotally mounted to its rearward end. Rolling members are mounted along the bottom of the floatation frame and tractor so that they may roll along the mobile frame. The floatation frame has floats along its rearward end and the tractor has a brake member to lock the tractor at a location on the mobile frame with a floatation member connected to the brake member for actuating the brake member when the floatation member is immersed in water by the floatation member floating upward, whereby the mobile frame may be rolled into the water to immerse its rearward end, and the brake member may be released to allow the tractor and floatation frame to roll rearward on the mobile frame into the water until the floatation member of the brake member is immersed and floats upward to lock the brake member, thereby locking the floatation frame and tractor rearward on the mobile frame with the rear end of the floatation frame afloat on the water.