ELI5: How can the sea temperature be higher than an unheated swimming pool that is shallow and in direct sunlight? We're used to the Med temperatures. You might be talking water temp of about 20. Personally I find after a while in my local pool I am starting to feel warm, however in the unheated pool I felt completely comfortable, not warm not cold. The air temperature in the pool room will need to be kept at a similar temperature to the water to minimise evaporation causing water loss and excess humidity, and to ensure that swimmers don’t become cold too quickly once they exit the pool. 10. Unheated pools were no prob for us in June - yes you have the initial - that's not a bath feeling, but then its actually very refreshing, especially when the air temp is in the 40s,