We are not from the area, but were going to be somewhat local that day, so were looking for an easy paddle in the area. I consulted a MA paddling book, and the reviews on Paddling.net and we settled upon the Assabet. I again consulted both sources in choosing where to put in...which was near Boon/Sudbury Road - not far from Honey Pot Hill Orchards. There are put ins and parking spots on both sides of the river...we chose the larger lot just over the bridge, as there seemed to be less algae to contend with.
The algae was not smelly, but it definitely took away from the natural beauty of the river. Perhaps it was worse due to a shortage of rain? The more bothersome aspect, and the point that made me rate this paddle as "moderate" was the seagrass. In my many years of paddling, I've not been as "weighed down" by the seagrass. It is so thick and ever-present, that it drags on the bottom of the boat, and gets stuck on paddles with nearly every dip.
However, I would recommend this paddle during a time of higher water. There was little if any development along the banks, and on a summer Tuesday, we had the river to ourselves - at least, we were the only humans we saw. The birding was really nice - with many spottings of great blue herons, swallows, swans, little green herons, red wing black birds, king birds, as well as a king fisher and a hawk. There were many turtles coming to investigate the yaks, as well as sunning ones. The breeze was lovely, and the water pretty flat.
Our original journey took us South (to the left after we put in). On our way back, we went past the Sudbury Road bridge aways toward the direction of the dam, and that way seemed wider, with less sea grass to contend with. All in all, a lovely day, and easy parking accommodations.
The bridge over the river at Sudbury Road near Boon Road provided parking on both sides - one had room for 1-3 vehicles, the other, could accommodate 5 or so, with considerate drivers. Not toilets.
We were not far off of route 495....we coordinated our gps to the intersection of Whitman Road and Boon Road in Stow, and watched for the bridge over the river.
Not recommended during very low water - drought conditions.
Quiet Water by Wilson Hayes.