I watch a You Tube channel called ‘Tiny Cabin Life’ and he spends his time camping and paddling around our Great Lakes.
He finds TONS of these ‘cave writings’ on walls all over the Midwest that were obviously NOT underwater at some point. Mainly, they seem to be messages to fellow travelers about SCARY animals in the area or an upcoming water rapids, etc.
So interesting to think of all the people that came before us and left their mark. :)
And under the Lakes for that matter.