If you aren't familiar with letterboxes - THE STAMP IS NOT SWAG and should be left in the cache.
This is no walk in the park; you'll have to earn this one by braving some rough terrain! If you have swamp boots, this might be a place to use them if there's standing water.
If you're wanting a more traditional letterbox experience with counting paces and using your compass, try visiting Zoe & Daisy's Woodland Trail Letterbox about 10 miles from here (GC5MKEH). Like this one, you'll need your bug spray and maybe boots.