One interesting calculation is to imagine a place with plentiful water and plentiful energy (and I mean lots!) and another place with a severe drought. One option is to send water tankers. Would it send more per tanker if we sent liquid hydrogen and liquid oxygen and recombine them? (incidentally you could transport some of the energy as well as it is exothermic but it is a damn silly way of doing that!)

The actual calculation is left as a exercise for the reader. But I warn you you need understand moles before you start.