This article examines shifting methods of plankton research within contemporary oceanography through direct participatory engagement on a ten-day research cruise off the Santa Lucia Escarp- ment in February 2025. As a feminist visual science studies researcher, I reflect on how seasick- ness, sensory immersion, and embodied participation shaped my experience of plankton sampling and reveal the entanglement of oceanographic knowledge with its contexts. While remote sensing technologies – such as satellites, digital twins, and remotely operated vehicles – are increasingly shaping oceanography and producing intensified modes of ocean quantification, I argue that tactile, physical sampling methods remain indispensable in plankton research. Rather than being supplanted, these transform into ground truth methods: observed and situated instances of contact between plankton and scientist used to calibrate, validate, and enrich remote sensed data. By juxtaposing physical collection methods with abstractions of remote sensing, I demonstrate how different technologies generate distinct ways of seeing plankton. Drawing on feminist, visual, and disability theories of science, I emphasize that oceanographic research, even when using remote sensing, is inherently embodied, situated, and coproduced through constant acts of negotiation with the ocean itself. Ground truth methods, I contend, are essential hinges that tether remotely sensed ocean data to direct, embodied ocean encounters.