I took a nap shortly after I arrived to the sailboat and awoke as the sun was setting, hungry and a bit cold. In the summer, the water gets downright warm and adds to the heat inside the sailboat; but in winter the opposite occurs. The cold water permiates the hull and cools the boat. At sunset it cools fast. This sailboat has several options for heat, depending on whether I'm on shore power or not and the temp. I won't be uncomfortable tonight and I've got coffee fixings ready for the morn.