Jeff Koseff focuses on the interaction between physical and biological systems in natural aquatic environments, and in particular on turbulence and internal wave dynamics in stratified flows, transport and mixing in estuarine systems, phytoplankton dynamics in estuarine systems, coral reef and kelp-forest hydrodynamics, chemical sensing in the marine environment, and coastal upwelling processes. Long-term research projects include understanding the transport of mass and energy in estuarine systems such as San Francisco Bay, and understanding how the coral reef systems of the Red Sea and Hawaii and the kelp forest systems of California function. 

More recently, at the 2011 Civil and Environmental Engineering graduation ceremony, Koseff received the Eugene L. Grant Award for teaching in recognition of "his continued dedication and excellence in teaching as voted by the students of the Department." Eugene Grant was a long-serving and highly distinguished member of the faculty at Stanford. The award was established by his students to honor his contributions. Koseff also received the Grant Award in 1995.