Pullmyfinger, your comparison is utter nonsense. Spoon is designed to hold liquid. Fins are designed to move liquid. You don't push fin perpendicular to where you go but at certain angle. Fins should be pushing water in certain direction based on their design.
Airplane wing is not split and provides decent lift. However if you observe an eagle wing you will see certain small splits at the end of weathers. How much you want to bet that eagle wing is more efficient in providing lift than airplane wing? If we had better way of imitating eagle wing on an airplane I am sure we could improve the efficiency and design.