Imagine this: you go to the seaside, you’re a bit hot from the Sun, while the water is a bit cold. How to enter?
After some practice, I found out that the best solution for this is to first enter the water quickly, close to the shore, lower yourself into the water so that you are fully wet, and go outside. Stay in the sun & wind for a while, and you’ll feel very cold. Stay like this for a minute or two. Go back to the sea. Now you will not feel the sea as cold as before.