Abstract: Understanding the motion of small bodies at a fluid interface has relevance to a range of natural systems and technological applications.  In this talk, we discuss two systems where capillarity and fluid inertia govern the dynamics of millimetric particles at a fluid interface.  In the first part, we present a study of superhydrophobic spheres impacting a quiescent water bath.  Under certain conditions particles may rebound completely from the interface - an outcome we characterize in detail through a synthesis of experiments, modeling, and direct numerical simulation.  In the second half, we introduce a system wherein millimetric disks trapped at a fluid interface are vertically oscillated and spontaneously self-propel.  Such "capillary surfers" interact with each other via their collective wavefield and self-assemble into a myriad of cooperative dynamic states.  Furthermore, the capillary surfer system has inspired the development of an untethered robotic version, the "SurferBot", which will also be presented. Bio Daniel M. Harris is an Assistant Professor of Engineering at Brown University in the Fluids and Thermal Sciences group.  Before joining Brown, Dan was a Postdoctoral Research Associate and Lecturer at the University of North Carolina at Chapel Hill in the Department of Mathematics.  Dan received his B.S. in Mechanical Engineering from Cornell University in 2010 and his Ph.D. in Applied Mathematics at MIT in 2015. Dan’s primary research interests are in interfacial phenomena, microfluidics, and transport phenomena.  His research involves an integrated experimental and theoretical approach.  Dan has also received numerous awards for his scientific visualizations, including being selected as the winner of the 2016 NSF/Popular Science Visualization Challenge in Photography, as well as being a five-time winner of the American Physical Society’s Gallery of Fluid Motion.