If each human on earth were to drink the recommended amount of water per day (1.9 liters), it would take them 259,931,901.5 years to drink 1.2348E21 liters (the amount of water in the oceans). This is assuming, of course, that each human, including babies, would have to drink 1.9 liters a day, all the water in the ocean was drinkable, and all water that was drank by someone would not find its way back in to the ocean.