The phenomenon you’re talking about being cold when you get out of the pool is exactly the same mechanism that makes you cold in wet clothes. Would you rather be naked and dry or naked and wet in the cold?

I suspect you weren’t swimming in winter… See “core body temperature”.

I would agree with you on cold and wet cotton being worse than synthetics, if you have to wear it dry. When cotton gets wet and it’s cold, you need to get out of the wet clothes and put on something dry. This does make cotton a poor choice cold, damp days, especially when some sweating is involved. I never could figure out why someone would want a cotton sweatshirt unless it’s to use as a towel. I have a few, but only wear them while working. I’m not really a proponent of cotton and I think that way too much cotton clothing is sold by the low end stores. It’s probably just that cotton is so much cheaper. I can’t stand cotton flannel and would much prefer acrylic flannel, but it’s so hard to find. Acrylic flannel shirts, sweaters and socks are nice and warm. The flannel holds up fairly well. Polyester fleece is nice and warm, if on the heavy side. I do like 100 wt. fleece for long underwear and sleep sacks. It’s got a nice feel. It’s the fire resistance of cotton that is important for me and a cotton outer layer over synthetics has worked best.

Actually cold and wet cotton is much worse than cold and wet synthetics or wool as cotton takes longer to dry and actually will take heat away from the body. The fibers collapse more, too.

While cold and wet is indeed bad..I’d rather be wearing a fleece than a cotton hoodie as I know the fleece fibers will not collapse as much, will help retain heat and will dry quicker.

Finally, and this is just preference, even when I was back in humid New England, I never really did care for a straight synthetic shirt in the summer. YMMV.