Since 1 gallon equals 90,840 drops and 1 Olympic sized swimming pool has 660,430 gallons, there are 59,993,461,200 drops in an Olympic size swimming pool.

The pool is standard Olympic size: 50 meters The pool is standard Olympic size: 50 meters

FINA sets the standards for the size of Olympic pools. The volume of an Olympic-size swimming pool is 660,430 gallons or 88,287 cubic feet.

I am assuming by professional, you mean Olympic size. An Olympic size pool is 50 meters. The most common lap pool is 25 yards.

the 1st olympic swimming pool was in 1899.