Marine Exhausts manufactures several sizes and types of Water Separators. To work efficiently they have to be sized to the velocity of the engine exhaust flow. See diagram for sizes.
Usually fitted to gensets, they are another silencer once the water has been separated. You can sometimes use a smaller outlet exhaust hose. Generally, a single water lift and genset with water separator can silence an engine by approximately 90%.
Water separators are not recommended for high revving engines unless sized correctly.