Lets use lake Superior as an example
This lake has a capacity of roughly 12100km^3 or
1.21 × 10^19cm^3

A normal male can ejaculate 2 to 5 ml of sperm so lets use the lower bound of 2ml or 2cm^3

So thats simply 1.21/2 × 10^19
Or
0.605 × 10^19

6.05 × 10^20 human males
QED