Hello kourkoubini,
I've also seen photos of a place that seems to meet your description:
I found them at the website of the youth-hostel in Plakias [
http://www.yhplakias.com/index0.html]
I think Chris [the master of the house of the youth hostel] can show you the way!
Asking the forum I got a reply from wakefossil :
Maybe it's the place where the drinking water comes from in Kourtaliotiko Gorge?
But that's only a vague presumption.
You can check it out next time you're there: In Kourtaliotiko Gorge there's a large parking area and a very small parking bay (on the right side of the road right at the beginning of the gorge when you come from Plakias). At the small parking bay a path starts that leads downhill to a small chapel below the road and further to the springs/waterfalls. Very nice place. Maybe the place in the pics is below the waterfalls (I didn't check if there's a way to get there). There's also a gravel track that goes off the road on the right hand side before the gorge (with a sign to some appartments, forgot their name). Maybe it's somewhere there...
But, as I said before, that's only a vague presumption.+Last week we went up the river from Preveli Beach as far as possible [with our kids] and found some similar places and swam in wonderful refreshing sweetwaterpools...
Please let us know, if you find the place.
shinaria