A water intake open cavity drum for ponds, which includes a drum body with a lower portion defining a cavity and an upper portion defining a cavity in fluid communication with the lower portion cavity but having less volume than that of the lower portion. The drum includes a plurality of stabilizing feet, at least one water inlet disposed in the lower portion, a water outlet disposed from the upper portion, and a venturi interposed between the water inlet and water outlet. Filtering media is disposed in the cavity, and when a pump is applied to the water outlet, a vortex is formed in the drum body interior which rapidly circulates water throughout the filtering media before it passes out the water outlet.