In Alexandria Bay, NY or Gananoque, ONT, you can ferry through the St. Lawrence River between the US and Canadian border to explore the Thousand Islands region. After exploring the scenic overlooks, walking down the dock, shopping in the stores, and enjoying a street magic show in Alex Bay, we took the two nations tour (the most popular tour) offered by Uncle Sam’s Boat Tour (https://usboattours.com). There is free parking available (even for RVs) at Uncle Sam’s.
For two hours, we cruised along and learned about the region and its thousand islands (1800 or so of them). The most famous of these islands is Boldt Island (http://www.boldtcastle.com/visitorinfo/), which requires separate admission to tour the castle, yachthouse, and grounds. Boldt has a unique and romantic history and the grounds are pristine and stunning. We also heard about other islands and homes which are owned or formerly owned by well-known or wealthy families. A highlight for the kids was the opportunity to captain the ship for a short period and receive a certificate from the captain. We really enjoyed the cruising through the Thousand Islands region and exploring the scenic town of Alex Bay. It was well worth the half-day detour here.