I notice a few things that make me sceptical of the picture.
To me their dress is odd. Why are they dressed as they are, for swimming? Two women with sunglasses on, everyone seems to be dressed in regular clothing ie no swimsuits - the child in the foreground appears to be wearing a tshirt and the smaller one in pink appears to be fully dressed right down to shoes or booties.
The picture is over exposed and the colouring seems way off. It reminds me of an old Polaroid, but the pic was taken in 2014. Does a digital take this bad of a picture? Maybe, but the pinks and greens just seem weird. And then they id the splotch as a teenage girl? Imo that’s definitely pushing it a little. It may be a bulbous shape, but to say it‘s a person? It does look like a double exposure.
Then when the supposed follow up details are that a girl drowned in the exact same place at almost exactly 100 years ago, that’s really where I roll my eyes. If it is a local swimming hole, I can pretty much be sure at least one person has drowned. Unfortunately that is not uncommon.