Not much. It would actually take hundreds of thousands of years for the ocean to drain. Even though the opening is wider than a basketball court, and the water is forced through at incredible speeds,[2] the oceans are huge. When you started, the water level would drop by less than a centimeter per day.

How long would it take to drain the ocean?

With a total volume of water throughout the ocean of 1.3 billion cubic kilometers that would give us a grand total of more than 80 trillion years to drain the entire ocean through said bathroom plug. “Or, to put it another way, almost 6,000 times longer than the entire universe has been in existence,” as Aldridge says.

What if all the water was drained from the ocean?

Well, without the oceans, the world loses 97% of its water. The small amount of liquid left wouldn't be enough to sustain the water cycle. The pools of drinkable water would evaporate pretty fast. In a matter of days, people and most animals would die from dehydration.