If the itch is driving you nuts, try ice packs on it. It was the only thing that worked for me when I had "too many" sand fly bites. Benadryl also helped some, but ice on the affected areas helped most of all.
I'd say your reaction is not from the ablative bottom paint
, or you'd have the rash on the rest of your exposed skin, and that's not what you described. Obviously something irritated it, something that you've encountered before. Interesting that the rash is not where swim clothing
might have trapped it, just on some areas of exposed skin.
The suggestion, above, to use betadine, I think is excellent. We've used it to prevent skin infections in tropical areas for years, now, and the only tropical skin infection either of us ever had was one scratch that the flies got to before we got back to the boat!. So, keep infection away; take Benedryl for the allergic reaction, and use soothing cream on the itchies, with ice applications as needed to preserve sanity. ;-)