"Chlorine is an oxidizing element! When it reacts to metals naturally occurring in water, it can give your hair a beautiful seaweed color that . . . nobody actually thinks is beautiful," says Cash Lawless, a celebrity stylist. "If you think a swimming cap would ruin your look (totally understandable) use a protective shield before exposing your hair to sun, salt, and chlorine."
Lawless is a fan of the Rinzu PROTECT Spray by SEVEN haircare ($28), which provides a "perfect base layer of protection."