If the ram pump works and does something useful with a naturally available resource that would go to waste otherwise, why would you not do it? Surely as you say, there is a decrease in efficiency when operating underwater, but the ram pump is only ~50% efficient at best in any case - did you let that put you off too? "Oh, ram pumps waste 50% of the available energy, you should't bother about using them"? If it can supply a useful amount of water reliably while under water, does efficiency matter? One of my rams is effectively under about 1ft of water all the time (because I catch the waste spill). It has performed without failure for comming up two years, pumping 1500l/day up to a height of 50m using a head of 1.8m. Hardly a waste of my effort considering it consists of approx $100 worth of plumbing parts.