Many aquatic environments are characterized by regions where water density varies over depth, often due to temperature or salinity gradients. These ‘pycnoclines’ are associated with intense biological activity and can affect carbon fluxes by slowing the descent of particles. Despite this, the fundamental fluid dynamics of settling and swimming in a stratified fluid have remained largely unexplored. I take first strides into this area by rationalizing the effects of stratification by conducting a broad, in-depth investigation on the fundamental hydrodynamics of small organisms, settling particles, and rising drops. These results demonstrate an unexpected effect of buoyancy, potentially affecting a broad range of abundant processes at pycnoclines in oceans and lakes. Bio: Dr. Ardekani is currently an assistant professor at the Purdue University and is the director of the Complex Fluids and Multiphase Flows Laboratory. Prior to joining Purdue, she was an O’Hara, C.S.C., Assistant Professor at the University of Notre Dame and a Shapiro Postdoctoral Fellow at the Massachusetts Institute of Technology. She graduated from University of California Irvine with her Ph.D. in 2009. She received the Society of Women Engineers and Amelia Earhart awards in 2007, Schlumberger Foundation faculty for the future award in 2009, NSF CAREER award in 2012, and PECASE in 2016.