Snakes
Common Watersnake
This is one of the most common snakes in NJ, inhabiting freshwater streams, ponds, lakes, swamps, marshes, and bogs throughout the state. This snake will likely retreat from you, but if you have to push your luck, this bad-tempered critter can give you a nasty non-venomous bite, and is likely to hold on for quite a while. All snakes are good swimmers, but this one actually likes the water.
-- Wikipedia
Other Snakes
New Jersey has a lot of other snakes, only two of which are dangerously venomous. Unless you are an expert, it is best to leave any snake alone. Garter Snakes can also be found in and around water, and have recently been found to be venomous, although their bite is about as toxic as a bee sting.
-- Wikipedia