Oysters, like the vast majority of sessile marine invertebrates, shed sperm and eggs into the water column where fertilization subsequently occurs. The fate of the gametes depends on their passive movements at various scales in a high-viscosity environment, the longevity of the sperm's ability to affect oriented movement, the rate of sperm movement toward the egg target, and the ability of sperm to effect fertilization. Oyster sperm swim in a helical pattern with a mean forward progression velocity of 0.057 ± 0.010 mm/sec (SE; n = 25) with the 95 percentile range extending from 0.036–0.078 mm/sec, a value comparable with that reported for echinoderm sperm.