Abstract: Apparatus for protectively enclosing and/or treating the submerged portion of a body floating on a surface of water, such as a boat hull, to prevent or reduce the growth of marine organisms on the submerged portion. The apparatus is formed of a generally rectangular frame having a depending water impervious envelope attached thereto sufficiently large to enclose the submerged portion of the floating body. The frame is formed of hollow tubular front, side and rear members with the front member being filled with floatation material which maintains the front member floating at all times on the surface of the water. Pump means are associated with the frame, preferably mounted the rear tubular member, with the pump adapted to pump water into the side and rear tubular means to cause the rear member to be submerged and moved pivotally downwardly about the floating front member so that the floating body, such as a boat, can be moved across the submerged rear member into the area defined by the rectangular frame.