No, New Jersey Does Not Have Water Moccasins
I already see the comments flooding in telling me I am wrong and that people have seen water moccasins in New Jersey. Usually, the statement goes along the lines of, "I've seen a water moccasin. I saw a black snake swimming in a lake/river." First of all, just because a snake is in water does not make it a water moccasin. Also, water moccasins are not all black.
I spent my childhood around snakes, volunteering at Cattus Island County Park in Toms River. I have spent most of my life fascinated with these reptiles, which is why it drives me up a wall when people tell me that there are water moccasins in New Jersey. Of course, could a water moccasin find its way up here? Yes, I mean there was a beluga whale in the Delaware River a few years ago.
Water moccasins are actually cottonmouths, also known as swamp moccasins. They are found in the south east, preferring a warmer climate.
We have a few states as a buffer zone between New Jersey and the states where the cottonmouth is found. Could one find their way up to New Jersey? Like I said before, yes, but it's not all that likely.
New Jersey is home to two venomous snakes, venomous not poisonous. There is a distinction between venomous and poisonous.
Here in New Jersey we have the copperhead, which is mostly found in North Jersey and is labeled as potentially at risk (not quite a threatened species, but monitored):
We also have the eastern timber rattlesnake, which you may find in South Jersey and is endangered:
For reference, this is what a water moccasin/cottonmouth looks like:
Whenever I hear someone say they saw a black snake swimming in water, my brain immediately goes to one snake in particular that we do actually have in New Jersey. The black rat snake is found all over New Jersey and they are great swimmers. They are almost all black, with a few flecks of white along their back and a light belly.
New Jersey is home to a water snake that can easily be confused with a cottonmouth, with similar coloring and an affinity for water. The northern water snake is confused with both the water moccasin and New Jersey's copperhead. It is common for non-venomous snakes to have similar patterns and colors to venomous snakes to ward off predators.
So if you see a snake swimming by, don't panic. The odds that the snake is venomous is on the lower end and the chance that it is the water moccasin is slim to none.