If the bottom is not excessively muddy and it is close to shore, just rent a wrecker, run a line to the bug and tow it out of the water.
Salvage laws vary from state to state and in some cases from municipality to municipality. I know on one of the rivers where I dive looking for items that fell in the water off what used to be a pier for a trading post from the early 1800's that if I bring an obect out on one side of the river, it automatically belongs to the city. If I bring it out on the other side, I can keep it because the city on that particular bank has no law covering salvage. This normally means everything gets hauled across to the other side of the river.
In general, if you find something with a title, you don't own it, but you are entitiled to a salvage fee. This is normally about 20% of the items value. If the item is pretty hopeless in terms of restoration potential, you will often get it by default.
In one case I found a motorcycle that had been stolen and then dumped off a bridge. It had been under water maybe a day and a half and was in excellent shape. I recovered it with the intent of rinsing it out, drying it and lubricating the interal parts to prevent corrosion but was unable to do this as I made what turned out to be a mistake in calling the police immeditately to report the find.
They insisted on immediately taking it into custody. About 3 months later they called and said neither the owner or insurer wanted it and that I could have it. They obviously made no effort to prevent any corroison and had simply parked it in a warehouse. One look at the corroded remains was enough to prompt me to advise them that I didn't wan't it either and that they could have the burden of throwing it away.
If you salvage a car for the owner or their insurance company, agree on the recovery fees up front. This usually means the car sits a few days while the details get worked out. I normally charge $200 to show up and $100 per hour after that for salvage or repair work.
