Is an evolution of this: https://www.GTA5-mods.com/maps/franklin-s-Lake, I had created to do a test on the water running and I took just a couple of moles to see how it worked, but it was a shame to leave it that way.
Now with a little more calm, I added a beach, located new bar, a floating platform for concerts, disco and islands, and created a mega Party on the Lake.
Download GTA 5 Franklin's Lake Party
Before opening the game, run OpenIV and go to edit mode, Navigate to common.rpf/data/level/GTA5
(BACKUP water.xml in case something went wrong)
And then replace it with the one included in the archive.
Then open game and load the franklin_Lake_Party file with the editor.
You need Map Editor by Guadmaz https://it.GTA5-mods.com/scripts/map-editor,
F7 -> load -> xml -> franklin_Lake_Party