The tree shows how high up the water reached in the "1 in 100 year flood event". The nail shows the height... stand next to it and look over the paddock and imagine how much water that must have been! If you are also finding other Bearii caches, take a look at the Strawbale house; well that was built above the flood level (good idea, I imagine, mud and straw don't't hold up to flood water too well) that this tree indicates; its hard to believe, given how flat it is here. Over time the tree is growing over the markings. You can still see part of the engraved words of history. The container is small and there's no need to damage the tree in any way to retrieve it. The container has no room for swaps and you will need to bring your writing stick. Please take care when parking off the road and you will need to keep an eye out for local traffic, geokiddies/beasts also.