I feel sorry for them, the worst I ever had in my pool was one of these:
It's front bumper went through the liner so there was not a big fight to clean up the water at least (it was a different model year with a bar style bumper), the scuff marks from it going in are still on the coping. The real amazing thing about the whole incident is it just cleared the double french doors (well the doorway), sheered the doors off at the hinges, but did not break the glass panes.
p.s. It looks like these things happen much more often than you would think, while googling the video shown above I found 2 other incidents of cars in pools in the last 2-3 weeks, one other in California and one in a hotel pool in Florida.