Water ETF
  
See: Exchange-Traded Fund (ETF).
And yes, there are ETFs just around water. If Dasani weren't owned by Coke, it'd be one.
A water ETF might also include a pipe company, transport, water witches, and maybe a rain dancer or two, were they publicly traded companies. Utility companies that deal in water are also probably part of the mix in any given water ETF.