I say a boat. If the engine dies, so what, usually. In an airplane, if the engine dies, you have a serious problem. Also the same price gets you a lot more room in a boat than a plane. Just sayin. And a nice place to sleep when you get to your destination, if you happen to have one in mind. Just cruising is very common in a boat. Not so practical with a plane.
All the regulatory crap with owning an airplane and all the required maintenance gets pretty expensive. Not that owning a boat is simple or cheap, but it is simpler and cheaper to have the same amount of money in the purchase of the boat than the plane. And with a boat, the fuel bill is way smaller. If you sail, then you are only running a genset and burning a couple gallons a day, typically.
OTOH, if you have to go from say New Orleans to Houston and you got an hour and a half to get there, you aren't going by boat. For business then, a plane has significant advantages, and a boat is rather impractical. Good place for meetings, though. Especially if you have some buxom and bubbly boat bunnies to help entertain the guests.