The small pond was no secret base; years ago, Shuxin and Cedric had received guidance from Seventh Great-Uncle right here, and it was also here that Shuxin had learned how to swim.
Back then, Seventh Great-Uncle had put a tremendous amount of thought into choosing this spot: it wasn't too far from Hogwarts, yet it lay just beyond the protective perimeter of the school.
To put it another way, Dumbledore, sitting in his headmaster's office, could not directly observe everything happening at this small pond.
Chapter 117