Glk350 engine block has a hole leaking what is the problem

You may find this hard to believe, but I can't see it from where I'm sitting. I can't see which engine you have either. Possible causes are coolant leaking from the weep hole on the bottom of the water pump and a leaking core plug. Beyond that you need a live person to look at it to see where the leak is occurring, if it's coolant or engine oil, and to determine what caused it and what is needed to fix it.