The Connecticut River, which forms the border between New Hampshire and Vermont provides many great opportunities for boating and canoeing. An excellent canoe trip is from Guildhall, Vermont to Lancaster New Hampshire. You can put in below the rapids, which are also just below the bridge from Northumberland NH, in Guildhall VT. You might find the area where Northumberland is on the map listed as Groveton instead. You'll know you're in the right spot if you see Perras Lumber or Guildhall village. You can paddle south for a day trip, and take out either at the bridge where Route 2 crosses the river, or about the same distance below, where a covered bridge crosses between Lancaster, NH and Lunenberg, VT. If you want to go even further, There's a boat launch in Dalton NH, about 5 miles more south.
There are lakes in Pittsburg, the Andriscoggin River north of Berlin, and a LOT more! I'm going to zip about and get some pictures and more info to include here soon!
Moore Dam is about 10 miles south on Route 135. There are high performance power boat races there in the summer.
There are also many lakes and ponds in the area with public access. Look in the map section of this web site. Refer to the NH and VT Atlas and Gazateers published by Delorme, or a state road map for more info.