The cache is a small container with some clever camo. I put in two pencils, but you may want to bring your own pen, just in case they break or get lost. (Also, if you just happen to have a pencil sharpener, and you just happen to notice that one of the pencils happens to need to get sharpened, would you please sharpen it! ) I highly doubt that the cache will be accessable in the winter. Be careful of muggles, as this is a fairly popular walk.
You do not need to leave the boardwalk to get this cache. Do not disturb the pond or nearby ground.