Pacific ocean is the largest ocean of the world. It's total area is 15 times greater than that of US. It covers about 30% of total surface area of the earth and has average depth of 4,000 metres. The depth of the deepest point is about 11 km. ( MARIANA TRENCH).

We can easily calculate the total number of water drops in this largest ocean (in 95% accuracy) as follows. Area of the ocean is 160,000,000 sq.km. 1 sq.km = 10,000,000,000 sq.cm. Now the total surface area of the ocean can be written as follows 1,600,000,000,000,000,000 sq.cm. Average depth of the ocean is 400,000 cm. Now the total volume of water comes as 640,000,000,000,000,000,000,000 cc. 1 cc or 1 ml of water contains 20 drops. Therefore total number of water drops in the pacific ocean is 12,800,000,000,000,000,000,000,000

Similarly we can calculate the total number of water drops that flow in the Niagara Falls in a complete day. The flow rate of Niagara Falls is 2 lacs cu.ft/second. We need to convert this into litres. One cubic foot of water contains 28 litres. so, the number of litres of water that flow in Niagara Falls for every second is 200,000x28=5,600,000 litres. There are 86,400 seconds in a day and a litre contains about 20,000 drops. So, the total number of water drops that flow in the Niagara Falls in a complete day is

5,600,000x20,000x86,400=9,676,800,000,000,000