This chapter examines how the submarine world of the ocean was perceived in the changing discipline of French Enlightenment geography. Instead of descriptions of mysterious depths, new life forms, or obstructed vision, geographical texts of the time attempted to work around the ocean. The water was not as important as what it hid. Thus to see underwater was to discover the invisible and render it understandable and legible in the same terms as the visible. The physical world became comprehensible when translated into a rational language that could see beyond all barriers.