I am not kidding, being in 100+ degree heat like that will definitely make you unable to cool off, better be inside and stay out of the sun, they tell you NOT to mess around. UV exposure strength is doubled than the actual forecasted value if you are in sand, water, or snow. I had done that in my younger years on field days and seriously regretted it once I realized I couln't handle hot days anymore. Even a few minutes of being directly standing in the hot sunlight no matter where would made me want to stay away.
This might be one of the many reasons why I never been down to the beach at all.