The aquatic ape theory is based on an observation that some physical attributes of humans seem to have been optimized with respect to aquatic surroundings. However, isn't the atmosphere a fluid just as any liquid? Fluid dynamics are pretty much the same, it's just the density that changes. Plus there's definately everyday interactions with liquids such as water, rain and sweat. Evolution optimizes everything it can, even the faintest traces of interactions with water become efficiently optimized and that's why we don't need to dwell in oceans to obtain "aquatic" features.