Why do guys on the swim team bleach their hair?

I’m just asking cuz this year and last year I remember a bunch of guys suddenly coming in with bleached hair that looked terrible on most of them like bleach blonde hair just dosent look right unless they’re pale.. I’m just wondering is there some story behind that cuz it’s every year in mid February like now. It just makes no sense like won’t chlorine make blonde hair green but won’t be noticeable on darker hair? So yeah Is there a tradition behind this or what?