Swim trunks are a type of apparel designed to be worn when swimming. As a result, they're frequently composed of fabrics that are engineered to get wet while being comfortable and hydrodynamic, so they don't obstruct the swimmer.
Here are a few reasons why it's critical to dress appropriately for the pool:
Street clothing (particularly those made of cotton) can carry toxins into pool from the air and water.
Cotton and other absorbent fabrics can degrade in water. These filaments have the potential to block pool filters, necessitating costly repairs. The finest non-absorbent fabrics for swimmers are Lycra and Nylon.
Any colorful or dyed materials might bleed into the pool, changing the water chemistry.
Is it ok to wear normal shorts such as Nike, Adidas? Well, if that's your preference, there's nothing stopping you from swimming in your exercise shorts.
But, consider this: You wouldn't run a marathon in hiking boots, and you wouldn't play golf in a flannel shirt. Athletic clothing is created and customized to provide you the ost comfort and performance for the sport you're doing.