Ultrasound is currently used for a vast range of non-destructive testing, evaluation and diagnostics in both industry and medicine. Its low cost and ease of use have allowed for many more applications to be investigated. Here we present some results indicating possible uses of low-intensity ultrasound in biology, specifically in the control of blue-green algal growth, and in the medical field to facilitate targeted increased drug uptake. Our results showed that pulsed ultrasound well within the clinical diagnostic range could be used to control algal blooms by bursting the gas-vesicles, forcing the algae to sink. Using continuous wave ultrasound we showed that it is possible to force ultrasound contrast agents to form clusters at a quarter-wavelength of the sonication frequency. These clusters contained more than 2000 microbubbles and could be forced to coalesce to form clusters large enough to block capillaries. Furthermore, using low-intensity pulsed ultrasound we showed that it was possible to force an ultrasound contrast agent, coated with a fluorescent dye, into cancerous cells.