"Just how can I get to Singer Castle or Boldt Castle?" is a common question, as they can only be reached by boat. Check out these sources for the answer:
Uncle Sam Boat Tours' Two Castle Tour is a popular way of getting to both castles from Alexandria Bay, NY. Call them at 800-563-8687 or click on their web link.
Schermerhorn Harbor, located at Chippewa Bay - Hammond NY, is very close to Dark Island and they can be reached at 314-324-5966.
Morristown Boat Tours, Morristown NY, offers tours to Singer Castle on their classic wood boat named the Morrisania. Call them for an appointment at 315-375-8213. (Post blog note: The Morrisania later was retired, so that service is no longer available as I have subsequently blogged.)
Rockport Boat Line (Rockport, Canada) also has a Two Castle Tour right from Canada. Call them toll-free at 800-563-8687 (or locally from there at 613-659-3402). Be sure to understand what is required to cross the border when coming from Canada. (The boat line will advise you on that).
Private boaters are also welcome to Singer Castle. Call ahead at 315-324-3275 or use your marine radio channel 16. (Note: Canadian private boaters must first check into customs at Heart Island near Alexandria Bay or in Ogdensburg. Please call ahead for more details.)
Disclaimer: This blog has no affiliation with Singer Castle or Boldt Castle or the boat lines. Absolutely check out all things with the primary parties before making any plans, decisions or actions.