Beating the proverbial dead horse here, but in the Glossary (Rule 0.9) :
Warship: Any surface ship that has an attack value (this would exclude naval transports and all types of aircraft carriers)
Surface ship: Any naval vessel that is not a submarine.
I agree with @Didier_de_Dax that « Surface Warship » is redundant since it’s already part of the Warship definition.
The distinction is useful for Aircraft Carriers, that are Surface Ships, but not Warships.
We could always suggest a correction to “Surface warships that go in the water (except for the bit that is above-water) but that you cannot land planes on” !