We don't recommend it - besides being impolite, weeing in a pool is injurious to health. The acid in urine reacts with chlorine (used to sanitise swimming pools) and produces toxic gaseous products, which can irritate our lungs and damage our respiratory system.

So, how do you think that scientists studied this chemical reaction? They collected samples of pool water contaminated with urine to understand the risks of weeing in pools. Then, they separated and tested the samples, all so that they could identify the compounds within. Next, they studied the compounds to understand how they react and impact our health. All of this distils down to one field of chemistry: chemical analysis.