Eastern Painted Turtle
Chrysemys picta
Size: to 6"
Habitat: shallow water over muddy bottoms
Notes: Also known as 'Sliders'. Likes to sun itself on floating logs. Sliders are not native to New Jersey, but the descendants of released pets are quite common.
Diamondback Terrapins are similar, but prefer a saltier environment, and are usually found in brackish water. This is the turtle that is most often eaten, and their numbers were once greatly reduced due to human predation, but have since recovered.
Box Turtle numbers are declining, so if you see one on a road or some other bad place, give it a boost to a better location before it gets killed. They are harmless and even tame.