Abstract: A portable dry ice holding container for cooling water contained in an existing swimming pool may include a buoyant cartridge with open first end and closed second end. A lid may be removably connected to the first end to form a cavity between the first and second ends. A unitary outer surface may extend between the ends, preferably having apertures formed therein for permitting water to ingress and egress the cavity. A handle may be penetrated through the outer surface, traversing the cavity with opposed ends remaining situated exterior. Dry ice may be removably seated inside the cavity and may interact with and lower the temperature of the water. A mechanism may agitate the water inside the cavity through linear reciprocation of the handle to increase a flow rate through the cavity. Such a mechanism may include a plurality of curvilinear blades rotatably coupled to the handle within the cavity.