Techniques for depleting target organisms in water include a waterproof transducer configured for ensonifying a container of water with low intensity sound at one or more ultrasound frequencies for a duration sufficient to prevent maturation of at least 90% of the target organism. In some cases the target organism is mosquito larvae. For example, a portable system for depleting target organisms in water includes a control system and a plurality of waterproof transducers. The system is configured for ensonifying a surface layer of water in an acoustic frequency range from about 40 kilohertz to about 100 kilohertz and in a power concentration range from about 35 milliwatts per milliliter to 100 milliwatts per milliliter for a duration in a range from about 1 to about 100 seconds.