Start at the Quabog Pond boat ramp and paddle to the left and under the bridge to enter the river. The journey may end after only a little more than a mile if the water level is too low late in the season, but if not you can make it all the way up to a dam at Lake Lashaway on rt. 9. To do this you have to take a right at the first fork (the left is a swampy dead end) and a left at the second fork (the right is the Sevenmile River)
You will encounter two small stick damns that advanced kayakers may be able to skim over if you build up enough speed. Otherwise you have to paddle up, grab hold, step out and over, and get back in (but its a fun challenge). If you take the right fork to the Sevenmile river there are many more obstacles like this that make it a difficult upstream trip.
The trip back is easier with the slight current helping you out, and when you get back you can kayak in Quabog Pond or cross the pond completely to South Pond which has a little beachy area to swim.
In total it takes about 2-3 hours.
On this trip I have seen a bald eagle, great blue herons, muskrats, turtles, and various small birds and ducks. There might also be otters and beavers (there are dams and beaver huts) but the only time I got more than a brief glimpse of a swimming mammal it was definitely a muskrat.