I see lots of water in the Mid west wind farms across the prairies.
Also how do you pump water from the ocean when the wind farm is miles off shore.
Hydro storage is perfect for hydro generation (if from running water not reservoirs). I haven't heard much about that for years though so may be it isn't practical at all.
Hydrogen is being chosen to be the preferred storage medium since you can compress it and transport it to where there is a market for it.
Batteries can be a temporary storage for excess energy but they are very limited and given the excesses being generated by new wind farms built to meet the peak demands of a grid, I see lots of potential for H2
In fact who are the best companies to invest in for electrolysis, compression and storage of H2?