The Moat Resolution:
 
 
 
 
Use the two planks, one of which is at the corner to help make an extension of the land, and the second one lies on top of the first one, thus being able to hit the corner of the other side. This problem involves a little abstract thinking and innovation  than the traditional, "direct attack" approach.
 
Click here to see the problem.
 
 
 
 
submitted by Alex Hernandez