I drive a defender 110 TD5 SW, Raised air intake, Wading kit, Winch on the front, and have had the whole chassis professionally waxoiled.
If you have a decent anchor the winch could be used to help extricate yourself, from a sandy beach, but I have never had to do so.
Although I dont have a boat at present, I have used this for towing boats, and trailers, and it will do it all day long.
Bad things are fuel economy, (dont even ask!) and it is a little uncomfy when driving for more than 5 hours or so, but on the plus side, I dont get stuck and the amount of room is enormous, it will carry 9 people too!
Not had too much problems with rust, but if you dont waxoil them they will rust, and particularly the older ones........