We all struggle at some point with your hair drying out or going a shade of green from swimming.
Prevention is always better than cure.
The best way to protect your hair from the sun, wind and water is to apply conditioner and then braid, plait or put in a bun/top knot.
The conditioner acts as a barrier. It coats your hair and slows the penetration of harmful chemicals.
The bonus is, it kinda acts like a treatment.
If you want to use this time to do a treatment then by all means please do so, simply wash hair first, towel dry, apply your fave treatment and tie it up. Just remember not to get it wet, then rinse and light condition when finished :-)