This one is probably easiest to get with a boat, kayak, or canoe. If you need to launch a motorized boat there is a PWA a little to the SouthWest of this parking lot. The water in the channel between the tip of the park here and the island is actually not very deep, you can probably wade or swim to it just fine. But the ground is all boulders, so bring good footwear. For that reason, I rated it as a 4.5T, a boat isn't required, but probably is a whole lot easier. Short folks may also wish to bring a step stool, I had to put this in an inconspicuous spot because it's clear the muggles frequent this island. BYOP.
As always, this cache is in a potentially dangerous location and seeking it is done at your own risk!