About a century ago this entire area on the Hudson's western shores was littered with islands. The most famous being Al-Tro Island Park (previously known as Lagoon Island Park and Pleasure Island Park), however there were many others including Lower Patroon Island, Patroon Island, Cuyler Island, Hillhouse/Breaker Island, Adams Island, Center Island (previously known as Magills Island and Starbuck Island), and of course, Green Island. Due to fluctuation of water level, access was limited to some, and eventually all except Center Island and Adams Island became landlocked due to the construction of I-787, which displaced the Hudson River in the 1960's.
As for the cache, it's on the Mohawk-Hudson Multi-Use Bike Path, located on what used to be known as "Cuyler Island" and somewhat near the informational sign about Hudson River Islands as well as a picnic area. This is one of those caches meant to bring you out to enjoy some little-known history and scenery instead of being too evil. That being said, look around before you make the grab or replace, because there are many muggles around on nice days.
You can access this area from either the Corning Preserve in Albany or the parking area in Watervliet. Hop on your bike or put on your walking shoes, and go out to enjoy your day with a cache or two!
There is little write-up online about these places aside from some general information on wikipedia and the Colonie historian webpage. If anyone has any further information on this island or others, please share what you know, it'd be interesting to learn.
Welcome to Cuyler Island!
Congrats on FTF: tenebrus