New York's water is delicious - and filled with tiny crustaceans called "copepods". (Making it possibly not kosher.) H&E stain the water and put it under a microscope and you'll find these little guys. Crunchy close-up after the jump.
(And completely harmless. Copepods are even known to eat mosquito larvae, so don't think of them as invisible shrimps that are caught in your teeth - think of them as invisible shrimps that make New York City's tap water taste fantastic. Like fantastic, quenching shrimp juice.)