Wow. Been a long time. I remember Christiansted being cool, lots of pastels on the buildings. I also remember almost causing car crashes trying to drive on the "wrong" side of the road... or was that Nevis? Now Nevis was AWESOME. Bring a passport.
ANYway, look up a dude named Mike Foster, owns and runs Coastal Air Transport ... uh, can I call it an airline? He has a big cessna and island hops people. He'll know. Say hi from Kathy, he's my godfather.
He hits Alexander Hamilton Airport (STX) and St. Croix Seaplane Base Airport (SSB).
Edit: Forgot!! He knows the best diving spots.