1. Figure 1 pint of pee per beach-goer.
2. Figure the astronomically low PPM of urine in millions (billions?) of gallons of beach water. Water which btw, is constantly in motion and recirculated.
3. Consider that urine inherently sterile.
So - what is the issue?
That said, it is probably of nutritional value to some species of ocean creature (one man's trash is another man's treasure after all).