My Pepere lives right across from this island and we often waterski and wakeboard near the island in the summers when we visit. Beautiful views and a nice swimming spot, the water is nice and warm(little sister has decided to attempt to swim around the island for her birthday next year).
This cache is accessable by both the trail and boat. It is located right near P4 off the Southern Tip trail. If muggles are staying at the camp site you may have to be careful in reaching the cache, although the location is not visible from the camping area. It should not involve any bushwacking to reach the cache. Please be careful to make sure the cache is tucked into its location well and is not too visible from any angle. To reach the island by ferry it will be $11 from Kamp Kill Kare and will involve a fairly long hike. Feel free to contact me prior to caching if you feel you may need additional hints. From a boat the terrain is not challenging.