A world away, and not so far at all. Paddle across the Nantasket Roads, as the channel is called, toward the outer islands of Boston Harbor. Little Brewster Island is home to Boston Light, the oldest in the nation. Or stop at Calf Island, a good spot for a walk, and continue across Hypocrite Channel to The Graves, and another light. ‘‘You can’t believe you’re 6 miles from downtown Boston,’’ said Mark Jacobson, of Charles River Canoe & Kayak. Charles River Canoe & Kayak, 2401 Commonwealth Ave., Newton, 617-965-5110, www.paddleboston.com.