wetted area

Short definition from Wiktionary

Noun

1. 1
   The total surface area of a vehicle which interacts with the fluid through which the vehicle travels: The total surface area of an aircraft.
2. 2
   The total surface area of a vehicle which interacts with the fluid through which the vehicle travels: The total portion of the surface area of the hull which is immersed in water.
3. 3
   The total surface area of a vehicle which interacts with the fluid through which the vehicle travels: The total surface area of the upper bodywork, wings, and radiator.