Swiming

The water under the bridge is toxic.

you ask the weirdest questions.
i'm glad life on my planet is so different from yours.
khairete
S.

are you using a body board or any type of flotation device?

Is it JUST your arm pits and under arms that are red? If so - I would venture to guess it's a reaction to either your suit (it's not fit correctly) or to a flotation device you are using...

Your suit is too tight and/or chafing from the arm movement... Throw a LIGHT layer of Vaseline on and see if it helps. Also, don't shave immediately beforehand, the chlorine could be an irritant to freshly shaved skin.

It's a common reaction. All trolls get skin irritation from water.

To too tight?
Pits freshly shaven?
Reaction to chlorine?

If you mean the armpit, then it's probably because of shaving and then getting in with open pores and a little skin irritation that reacts to the chlorine. If you mean the skin on the side, then it's from the wet bathing suit edge rubbing against it especially as you swim, lifting your arm and bringing it forward. So a different cut of suit might help.

If that skin has been roughed up by shaving or deodorant it might be more sensitive to the chemicals in the water.

Our pool uses bromide? Bromine? Something like that. Our swimsuits are not getting eat up and are lasting longer but I break out in a rash nearly every day.

Sounds like a chlorine reaction on sensitive skin.
Shower in the locker room (use soap) before you get home to get it off your skin soon as possible.
Do you shower before you swim (remove antiperspirant and/or deodorant)?
Maybe that plus the chlorine is irritating your skin.
Shower before swimming and again right afterward.