hydrophobically coating the surface of a submerged relatively high velocity moving object,
Will not prevent cavitation, which is generally the biggest issue, and might even increase it.
probably won't significantly change other physical constants such as Reynold's numbers.
understand that the water molecules are already travelling at an average velocity of the speed of sound in water, they can't slip past an object at that speed regardless what the object is coated with, so they will stop, and form a layer of water that is moving with the object.