Imagine a hot tub party where a married couple tests the boundaries of fidelity. A model who finds herself unaccountably aroused as she poses for a watercolour artist. A pool of water on a desert road and two lovers who know how to make the most of it. This is Aqua Erotica, a sensuous tasting of desire’s liquid, ecstatic other worlds. The first-ever waterproof book for adults that literally goes places you never imagined books to go…