river acheron; river adige; river aire; river arno; river avon; river basin; river birch; river blindness; river boat; river bottom; river boulder; river cam; river cocytus; river cooter; river dolphin; river gum; river horse; river kasai; river lethe; river limpet; river otter; river pear; river prawn; river red gum; river severn; river shad; river styx; river thames; river trent; river tyne;