This is a slide shot with a slide duplicator. Strong red cast. Can’t tell the film type without opening the mount, which I prefer not to do.
The original picture:
A first shot at it (convenient French flag in front):
The raw file:
Diapo000165.cr2 (14.5 MB)
These files are licensed Creative Commons, By-Attribution, Share-Alike.
Brigitte Bardot may or may not be hidden in the picture.
Exported unedited from Rawtherapee into GIMP, then did Auto Equalize. Seems to be pretty close but I can’t figure out why the water has reddish highlights
I could have played with this for ages. Still not happy this is my result with dt:
Ooo… nice photo, @Ofnuts, and looks a challenge. I’ll have a go later, but I think @Popanz has done am excellent job here.
@123sg A little typo with @Popanz. I agree that #3 is the most realistic slide-looking rendition so far, at least from what I can tell with my un-calibrated screens.
After applying auto equalize in GIMP, I edited this image with ART and following CTL Script.
Two tries at this image using GIMP. First one - using the colour cast reduction plug-in. The second, adding a slight tweak with Colours/Curves.
And yet a third try! Applied my saturation H M L plug-in to increase the saturation in high and medium regions to bring out the colours of the sky, roofs and flag.
For reference, here’s a stock photo of the harbor 1960ish, SAINT-TROPEZ HARBOR, VAR, FRANCE Stock Photo - Alamy
Horrible pic…
I’m not able to leave my fingers from it.
OK another attempt. Tried to keep it more warm, sunny and saturated.
Anyway, still not satisfied 
All done in dt, just some richardson-lucy sharpen afterwards with GMIC:
Inspired by
And sone further optimizations, including noise reduction and a slightly cooler white balance:
