A floating oil skimmer and gravitational separator system, consisting of a vessel adapted to be submerged in a body of water. Oil/water are drawn through the floating skimmer head by a water pump, pumping water through the skimmer head as water is pumped out of the vessel from the bottom of the vessel. The improved skimmer head design improves control of the skimmer head buoyancy and stability, thereby more consistently bringing oil/water into the vessel. An improved means of coalescence and collection of oil into the top of the inside of the vessel is also disclosed, where the oil once collected is then pumped out of the vessel for storage and the water is returned to the water body. Methods of manufacturing the system are also disclosed.