Using a funnel, add water to a glass bottle or stable plastic spray bottle.
Add the ascorbic acid.
Add essential oils (if using).
Put lid on bottle and shake to combine.
After swimming, spray the solution all over, including on hair.
Rub the vitamin c spray in, making sure to cover all of your skin. If the Vitamin C doesn't cover your skin, it won't protect it.
Shower as usual.