I have no idea what they are but they're less than 2 mm long, have 6 legs and no definitive segmentation. They weigh so little they don't break the surface of the water. Edit: They are Tidal pool arthropods - Anurida Maritima or Maritime Springtails. They eat muck and slime, prefer New England coasts & can breath underwater as their hair collects bubbles.
http://en.wikipedia.org/wiki/Anurida_maritima
