JUST A FIRST NOTE BEFORE YOU DO ANYTHING ELSE...This cache site is sorta...volatile. Not in a bad way, but as you read below in the comments, this cache site can sometimes be submerged in water, and other timess completely dry...Which is sorta cool, to me at least. It is all based on tides is my point. While sometimes of day Clam Rock may seem like an island 30 feet off shore, at other times there is a very comfortable walkway to the rock. So, if you don't want to make two or even three trips to the site, check your tide charts first. Believe me, it is not a good idea to be attempting this cache at high tide. I myself have not experimented with the island at various tides, so I cannot tell you the exact sweet spot for my cache, but I will try to find the best tide range to attempt this at. Try messaging other cachers on this to see what tide they got it at. Good luck on it, and check your tide charts.
My first suggestion is to approach the trailhead (Find Coordinates in Cache information) from the South, crossing the drawbridge over Eastchester Bay. The Trailhead will be on your right side, and it is quite hidden. It is a slightly steep incline, with a couple large obstacles in the way, but so long as you are prepared with good boots and long pants you should be fine. If you plan on bringing a car, you must plan ahead where to park and then how to walk to the cache (I suggest the parking lot before City Island a bit North of the Cache). If you plan on biking there, you will need someone else to watch your bike, or you will have to find somewhere to lock it up.
Once you reach the trailhead, just head down the mud path towards the underside of the drawbridge. There will be a few points at which the trail seems to go away, but once your each the sectio of the path patched up with dry straw, you should be good. my suggestion is to stick by the rocks, they provide protection from the mud and grass.
The cache is located on a huge boulder to the East side of the bridge. All I can tell you is that the cache is on top of the bridge, in at least 5 feet proximity of the given coordinate. It is not going to be obvious, USE THE HINT!!! and pay attention to detail.
Completed with my friend Matt and Joe