The Swan River (or Swan Pond River) empties into Vineyard Sound. It is a very winding, twisting tidal river that begins at, you guessed it, Swan Pond! There is a great kayak rental place on the river right on Route 28. They rent electric paddle boats and canoes as well. The river is greatly affected by the tide, but I found it passable even against the tide. There are a number of birds here, such as red tailed hawks, Great blue herons, egrets, and many geese, etc. The river is also alive with crabs and fish life. From the rental place, you can paddle to Swan Pond or out to the mouth at South Village Beach. If you're a fisherman, keep an eye out for feeding birds in the sound. There are many schools of football-sized bluefish around close to shore. The sound is usually paddler-friendly in good weather, but beware when the wind is up. If there are 2 to 3 foot 'peaked' waves, just stay in the river and enjoy the flat water. Good Paddling!!
No restrooms here, except for the rental place. If you don't have a boat, their fees are quite reasonable, especially for multiple day rentals.
There is a fee to park at Dennis Beaches. If you are there for a week, go to Town Hall and get a sticker to save money.
From Route 6 on Cape Cod, take route 34 toward West Dennis. Turn left at Route 28 and look for the rental place on the left, or keep going straight down Route 34 to Lower County Road and go straight across to South Village Road. Go to the end and park in the lot. The beach rarely has big waves and you can launch there.