Dinoflagellates are extremely important components of marine phytoplankton. They are motile, but relatively little is known about their swimming behavior or the physics of it. This project has three main objectives that address dinoflagellate swimming. (1) To obtain observations using a video-based computer-assisted motion analysis system that will aid in the development of swimming velocity models in response to light, temperature, salinity and nutrient concentrations. (2) To examine the time course of the biological terms in Stokes Law for dinoflagellates grown under a variety of environmental conditions using a variety of techniques. (3) To expand a newly developed random walk turbulence model to include a broader range of eddy diffusivity coefficients; water column stratification; various phase relationships between turbulence initiation and diel vertical migration; and various dinoflagellate swimming characteristics. The models developed will be very useful in understanding and predicting factors that account for the distribution of dinoflagellates in the water column.