marine layer

"The marine layer forms when relatively dry and warm air moves atop a body of cooler water. The warmer air close to the surface of the water cools and, thanks to its proximity to the water, becomes saturated with water vapor."
And so it was this morning. A cold fog shrouded the beach, but a half mile inland it was sunny and 9 degrees warmer!
Fortunately the layer dissipated after lunch and it was sunny and warm everywhere.