What a strange thing to see - those overlapping colors, the strange shapes that splattered and formed in the spots. It was enough to cause interest, and for the moment the sound of the falls is drowned out by a thrumming pulse. Mythris' Heartbeat, perhaps. It sounds strangely like the buzzing of a swarm of locusts with the thundering roar of a stampede of wildebeests combined. It sounded like the very essence of being wild.
The chunks of earth that tumbled down and then sank to the very depths exposed something else.
The rune suddenly had space, and then! -- it tumbled down, knocking off the edge of the wall and the uncomfortable sound as it 'PLUNKED' into the water. It sounded nothing like the rocks had. The rune was thankfully still visible, the roar of the falls restored now that the rune was released. You can still claim it - if you brave the deeper waters and are willing to take the risk.
Perhaps when you are done, you can draw your story for those who may come next. Perhaps even for the pale beauty who calls out now. Perhaps she has keen eyes; perhaps she had witnessed the rune. Hopefully, she wasn't so distracted by your expressive art attempts.