Stop River is a charming marshy tributary of the Charles River. We sat on stones at the put in and had a picnic lunch, enjoying watching the many birds flitting around.
We mostly had the winding river to ourselves except for when we took off and a handful of kayakers were just returning. We asked one person what he saw and he said, "Oh, just the usual: white-tail deer, geese, heron, turtles, birds, muskrat, beaver, and their dams."
We canoed on the mostly gentle river for about 2 hours and saw all the animals the guy had mentioned minus the deer and beaver.
My husband and I will definitely return.