Unlike the Bond original, which featured an enclosed passenger cabin, the modern version has an open top with the occupants exposed to the elements.
The Swiss car designer explained: "The passenger compartment is three square metres of air - you'd need to add about three metric tonnes of added weight to pull it down under the surface.
"That would give it the land mobility of a turtle."
The second reason for having an open cabin is safety: "Even at one metre depth, the water pressure would keep the doors closed so you could not get out in an emergency."