The difficulty in this cache doesn't come from finding it, but from solving the puzzle box inside.
You are looking for a large green ammo can that should be easy to find. inside you will find a decent amount of space for loot (my kids filled it with toys to start) and a puzzle box. inside the puzzle box is the log.
**Please be gentle when using the key to the puzzle box. The keys can be fragile. You shouldn't have to use a ton of force to use it. :)**