A crate would be worse off than a boat. There’s a reason a boat is shaped like a boat and not a shoebox. Even barges have one or more shaped hulls. I think everyone since antiquity knew this fact, hence the tradition of a boat-shaped object.
As pointed out before, a wooden boat that size cannot be physically supported, however even a box the size of a small boat cannot support itself in water, it would simply crack as soon as it got lifted.