Scale-dependent horizontal diffusivity at the sea surface is a controlling parameter for the trajectory and dilution of soluble pollutants and other tracers. A lightweight, low-cost GPS surface drifter with satellite telemetry, a durable low-profile hull, and a sustained operational lifetime of around two months has been developed, enabling cluster-style releases for pair statistics across a wide range of separation scales. Nineteen units were deployed from research vessel (R/V) Isabu during August and October 2024 at two energetic sites in the seas of the western Pacific and south of Japan. Relative dispersion from the trajectories yields scale-dependent diffusivity that rises from the order of 101 m2s−1 at 10 km to 103 m2s−1 near 100 km, with values of 2.7 × 101 and 9.6 × 102 m2s−1 for the western Pacific site and 4.3 × 101 and 1.7 × 103 m2s−1 for the region south of Japan. The empirically constrained curve for horizontal diffusivity as a function of scale provides a direct constraint for subgrid-scale mixing in coarse-resolution contaminant transport models and demonstrates the field readiness of the new drifter system.