The deep sea is the largest habitable ecosystem on the planet and remains one of the least explored, and subsequently very little is known about deep sea inhabitants, their behavior, and the limits and drivers for their survival. Ecomechanics, the multidisciplinary research field of the mechanisms that underlie organismal interactions and survival within their environment, has proven largely successful in terrestrial field and lab-based organismal systems, but has had limited applicability to deep sea animals. The reasons for this deficit is largely due to the technological challenges to access this environment for study, as well as limited instrumentation that can enable measurements of complex fluid and organismal motion and behavior at the required spatiotemporal scales. To partially address this need, we have recently developed and deployed an in situ lightfield imaging system named EyeRIS (Remote Imaging System). This 4000 m-rated instrument provides real-time 3D particle and surface visualizations, and is deployed from a remotely operated vehicle (ROV). Here we describe the first at-sea deployments of the system in the Monterey Bay National Marine Sanctuary, and share how the dynamics of feeding and swimming animals (e.g., squid, ctenophores, sea stars, coral) in the deep sea can be effectively studied.