The ocean has been rough for days. In some spots on the beach in our backyard, the breakers have reached 6 to 8 feet high. You can hear the roar of the ocean a long way off. You can see the waves breaking over the cays a mile offshore.
When I get into the ocean in these conditions, I get sea sick. First of all, visibility is not that good. Then the waves toss you to and fro. The waves pull you back, and push you forward, ten to 12 feet at a time. And then you rise and fall with the waves. Your snorkel barrel is swamped and you swallow salt water. And soon, due to the gyrating visuals, you are sea sick.
But there is another unpleasantness in the rough surf. The roily waves break off the tentacles of jelly fish. They are long and transparent. And for even hours and days after they have broken off the jelly fish, they can sting you.
When I first started swimming in the waves, I would emerge on the beach with these huge welts that stung like crazy. They always got me on the underarms, on my back, on my forearms -- essentially the leading edges of where you body touches the waves as you swim in the rough surf.
Eventually, I was stung so many times that I have become accustomed to the venom. The sting of the tentacles do not raise huge welts anymore. I get out of the water, and I idly notice a sting. By the time that I am at the beach entrance, I no longer feel it and the red marks on my skin are gone.
I still get stung a lot by the coral. There are little stinger things all over, and when I dive for golf balls and accidentally brush against it, it still stings. And I am not acclimatized to that. The stings cause the skin to slough off and I have a scab for a few days that leaves a small scar. My arms and hands are peppered up and down with war wounds from the coral reef.
I used to get stung by the spiny sea urchins as well. One day the spine broke off in my skin, and it irritated me for three days. Finally I googled "sea urchin stings". I was dismayed to learn that sometimes surgery is required to remove the spine. The same page stated that ordinary vinegar dissolves the stinger, and hot water neutralizes the venom. I immediately dumped out a bowl of vinegar and within two minutes, three days of pain disappeared. I held the lesion under hot water, and sure enough the venom was neutralized. Three days of suffering for nothing. Google is your friend.