A vortex system in the water near the sea surface has been inferred from collection into parallel rows of a positively phototaxic zooplankton population. Water velocity in the upper part of convergence planes of the system has been equated with estimated swimming speed of the animals....
Owen, Robert W.. 1966. "Small-scale, horizontal vortices in the surface layer of the sea." Journal of Marine Research 24, (1). https://elischolar.library.yale.edu/journal_of_marine_research/1064