The cache is NOT at the above coordinates, nor will you need to enter the water. However please be careful of tree roots and the waters edge. To get the coordiates you might need to think musically, we suggest the following piece.
When you get to GZ there is a field puzzle. Please take something magnetic with you. And please take care as it is handmade. If it gets broken don't worry, just let us know and we will replace!
*Thanks to Quirky Caches for bringing this idea to life*