I have heard about floating solar being added in India. There it was being used to cover irrigation canals. The big plus is that helps cut evaporation. But, you still need to add the infrastructure to connect it to the grid.
Fully Charged Show talks about a system in Portugal. It is floating on a reservoir which is behind the hydroelectric dam. That means it can share the grid connection with the hydro plant. It seems like a real win-win installation.