Yes I know. But the fantastic thing in that puzzle is just that! The solution is so simple you actually overlook it. I remember when I was a kid I spent the best part of two minutes thinking what to do to grab one of the knives that where just spread on the ocean floor, two or three meters away from Guybrush. When you eventually find the solution to the puzzle you've got that sensation of "No! It can't be so simple!" that's fantastic to me.
And if you wait five minutes, there's the "throw the knife in the water" joke.