hahaha boats float
yeah i don't think you can legally build a pit. i wouldn't go 6 feet either, more like 4 to 5. usually there are two ramps that "bridge" either side of the pit too. also, you would want a drain because water would definitely get in there. i guess it would have to be contained and removable for the bad stuff that would come out of your car. you should just make friends with someone who has a lift though! or get a forklift