I recalled my grandmother talking about a ferry boat that used to transport them across the river between our town of New Kensington and Tarentum on the other side before bridges. This beach was on the New Kensington side.
To me it appears that there are different folks in each photo. In the 1917 photo, below the people are close to the shore, it appears, but look at those dresses; I doubt they would have ventured very far into the water, surely that would hav weighted them down.. . The woman to the right appears to even be wearing some type of stockingn if that is a woman, I think they both are with children.