Experimental applications of pigmented nylon film were conducted in the Seattle metropolitan area in order to evaluate gas venting characteristics and instalation procedures. The material was highly effective in controlling aquatic plant growth, causing death and decomposition of covered plant materials in 30 to 35 days. Gas entrappment, ballooning, and lifting was observed with unvented material but this was overcome by placing venting slits in the material. A vent slit design of 12/meter2gave the best result. Installation of the film is straightforward and simple. Difficulties encountered with dense plant growth and soft organic sediments are described.