Hubby and I had a waterproof camera and a willingness to kayak, so we went looking for options. Enter North Shore Kayak. Every day at 1:30 (during the summer), they offer a guided kayak trip to Thatcher Island. Please note - this is a two to two and a half mile paddle one way, so be prepared. It is a three hour tour, so you have time to explore the island and rest before your paddle back (climbing a lighthouse is resting, right). Make sure you take plenty of water.
Call at least the day before you want take your trips so there is space and/or a guide available. You will be asked to arrive half an hour early to sign the waivers, get your PFD's and walk to the launch site. The waiver can be printed from their website before you go, if you like. Once all of the prep work is done, it is into the kayaks and a paddle around the perimeter of the harbor.
Once out of the harbour, you aim for the strait between the cape and Straitsmouth Island.
While passing you will see another lighthouse.
Once through the strait, you can see the Thatcher Island lighthouses.
Just outside the boathouse is a plaque with information about the island.
From the boathouse, visit the light house museum then go to the lighthouse for a climb.
When you are done exploring the island, it is back to the boats for a paddle back to the starting point with another view of the Straitsmouth Lighthouse.
I highly recommend this tour. Patrick was our tour guide and he was very patient with me as a novice paddler. Once on the island, he gave us the option of givings us the tour or letting us explore on our own. If paddling is not your cup of tea, there is also a boat tour that goes to the island once or twice a week. Information is available at the end of the T pier.