This is an extremely unique experience but could be challenging for some, at least in certain conditions. While the website says a fitness level of "Moderate" is required, I would recommend that you err on the side of caution when booking this tour as it could be more on the strenuous side of things. In our paddle we took a few short breaks but otherwise, we paddled for about 45 minutes non-stop in each direction (outbound was a bit choppy as well). Our hike was pretty continuous as well. In part, I think this was due to the very fit and enthusiastic participants in the group and I enjoyed the workout.
Nonetheless, this was a great experience with guide Eric. If in doubt, I'd recommend bringing some extra warm clothes, especially if there is rain in the forecast -- there is plenty of storage space in the (tandem) kayak. A spray jacket and dry bag are provided along with other safety equipment.
Dinner on the island was surprisingly tasty but the portions were not that big. Especially given the active nature of the tour, you may want to bring some snacks and/or have had a hearty lunch. Note that there are restrooms but no drinking water on the island.
At the end of the tour (when it started to pour), Eric took a few of us back downtown, which was greatly appreciated.
Come prepared for a bit of a workout and a sense of adventure and you'll have a great time!