One Thousand Ways to Make Money by Page Fox

a large pool or tank where, by a system of planks fastened to a central post, two bathers could go alternately up and down, one being in the water while the other was in the air, an arrangement like the see-saw which children are so fond of. It should have sufficient capacity to accommodate a number of bathers at once, and should be as near as possible to the sea, so as to be available by persons in bathing suits, who have already had a salt bath.