Most people think of frisbee as a casual form of relaxation between two people, or perhaps an alternative to throwing a stick for your dog to run and fetch. But apparently it can be a serious competitive sport, too, as I discovered when I wandered past two uniformed teams playing a "serious" game of frisbee on a grass field the size of a soccer field. (After uploading these photos, I was informed by a Twitter friend that they were playing "Ultimate Frisbee," which is played by competitive club teams in colleges across the country. Who knew?)

True, the uniforms consisted merely of a colored shirt, to distinguish the yellow team from the blue team; there were no helmets, hats, knee pads, or other forms of protection. It wasn't needed, because there was little or no physical contact between the players; they merely tossed the frisbee to other members of their team as they raced from one end of the field to the other.

All of this took place in Riverside Park, near a broad sidewalk that runs along the Hudson River, beneath an elevated section of the West Side Highway. This is located near 72nd Street, and many other New Yorkers ignored the frisbee while they lined up to take freely-provided kayaks out into the river for a quick paddle, or while they enjoyed lunch and a snack at an outdoor restaurant just to the south of the frisbee field.