No, I am not in Thailand, nor any other tropical region.

At the Mediterranean, I swam when day time coldest temperature was 11°C in air and luckily it was 16°C in water. No one nearby swim under that condition. I wouldn’t either if I hadn’t experienced it before.

It was mid April 2019 when I took a boat tour in southwest small town of Ölüdeniz in Turkey. Temperature was about 15°C and warm clothes were needed. At lunch time, the boat anchored somewhere offshore, and the water was beautifully clear and calm, but freezing cold. The guide indicated as OK to swim if one wished. Depth was about 30 meters, he said. Some jumped in the water, while screaming. I watched a bit, thinking since these people were doing it, I should try it. It was cold just by taking off the clothes. So I went down the ladder and got in the water slowly, feeling the cold invading from the feet. As I got hip-deep, I jumped. It was a sudden stimulate to the whole body lasted for about a second. Then it felt very cold, but tolerable.

Another time was early August of 2019 when I was at Kravica Waterfall outside of Mostar in Bosnia and Herzegovina. It was hot in air, probably 30°C, but the water was freezing even when it was just ankle deep. Some said it was 12°C. There are a lot of underground rivers in the country that flow to the surface at some places. This must be it. So I tried swimming for 15 minutes, feeling much colder than in Ölüdeniz.

So these two experiences tell me it’s OK to swim in the 16°C water. I do it whenever the condition is good: sunny, calm sea, clear water, and without medusa. An interesting sensation is that when there is wind the skin feels like being smeared with spices.

Reportedly, there are many benefits of swimming in cold water, including improving the metabolism, boosting the immune system, maintaining body shape, getting mental clarity, etc. More about it here

Cheers! Santé! Prost!