Northern Water Snakes can be found in the lakes and ponds of the Rensselaer Plateau. They are active during the day and at night and are most often seen basking on rocks, stumps, or brush. During the day, water snakes hunt among plants at the water's edge, looking for small fish, frogs, worms, leeches, crayfish, salamanders, young turtles, and small birds and mammals. At night, they concentrate on minnows and other small fish sleeping in shallow water.
Northern Water Snakes mate in April and June. They are live-bearers, which means they do not lay eggs like most snakes. Instead, they carry them inside their bodies and give birth to baby snakes, each one six to twelve inches long. A female may have as many as 30 young at a time. Babies are born between August and October. They have many predators, including birds, raccoons, opossums, foxes, snapping turtles, bullfrogs, and other snakes.
There's a lot written on the Northern Water Snake, one of the better write-ups is from the Yale Peabody Museum webpage on it. Note that "The species is not venomous, but will defend itself vigorously when cornered or captured. Defense may include defecation, spraying musk, biting repeatedly, and vomiting, but no venom. The species is generally very cautious and to avoid conflict will usually enter water on the approach of a human."
UntamedScience.com's entry is also pretty good, mentioning "Even though they are not venomous, watersnakes are considered an aggressive species and will bite if handled. If you do pick one up and get bitten, don't panic! Just treat the small wound like any other scrape or scratch (wash with soap, bandage if needed)."
Creepy -- no question -- but, they will leave you alone if you leave them alone. Thomas Tyning, Herpetologist, Massachusetts Audubon Society writes in his posting, THE NORTHERN WATER SNAKE ALONG THE CONNECTICUT RIVER, "Northern water snakes bite people just as often as chipmunks and bluebirds which is to say just about every time they are grabbed. With a large head, fairly massive jaw musculature, and a mouth filled with six rows of sharp, recurved teeth, water snakes can deliver an impressive defensive strike but only to those who lay hands upon them. And this isn't even true all of the time. I've been able slowly to approach some northern water snakes, carefully reach my open handbeneath their bodies, and lift them into the air, all without the snake becoming agitated or me becoming the recipient of a surprisingly strong bite. Sometimes, however, this doesn't work! Rather, enjoy water snakes from a short distance, watching how they go about their daily activities."
Northern Water Snakes are extremely helpful to people. They control populations of smaller animals, such as mice. Unfortunately, they are sometimes mistaken for Copperheads and Cottonmouths (also called Water Moccasins, which don't even live in our area), and killed. In fact, there are only three species of poisonous snakes living in the wilds of New York: the timber rattlesnake, the massasauga, and the copperhead. All three are uncommon and they are not water snakes.
If you see a snake, it is best to leave it alone. Never kill a snake without good reason, since they are so important to our environment. But... I think I won't grab them.