I also agree on Water as the third item, but not so overwhelmingly as to guess it before Dave weighs in. Dave, unless you see something else feel free to guess it provided both the above are blue.
Limousine - usually comes with a driver
Pilot - drives things
The third word is trickier. I like these best:
Maple - the wood that the heads of drivers (golf clubs) were originally made from
Undertaker - may drive a hearse
Glove - chauffeurs might well wear them
Don't see any good options for a 3rd. HOOD cause it's part of a car? POST being short for postman? I'd probably pass.
rho: Didn't think of MAPLE, nor of the golfing driver. Did JR4 mean to include the golfing definition in the clue? It probably wouldn't be difficult to find another word that fits PILOT and LIMOUSINE (vehicle?), so it could very well have been. Still risky.