The heat effect is surprisingly good for the thin material. I went in the Mediterranean only the shirt on 12m dive. Not hot but bearable for 30 min.
That with the "Fruit of" from the other review, I can not quite understand. I bought because of the comment XL (185cm 80kg) and the shirt is around the abdomen herrum very far. The weight belt hälts at the hip, but when swimming without belt inflates the shirt with water. Next time I would take L.
On and off for two goes much easier!
In any case the shirt has 1a sunscreen snorkeling, also high in the neck inside.