Fill it with gators!! 
Exactly. You could even generate revenue off of it and have it protected federally as a National Wildlife Refuge.
Much better than wasting money on a wall. God, people are fucking stupid. You can't jump over a wide ass moat full of gators and you can't dig under it and I am sure it would be cheaper to construct and maintain.
AJ, why would be opposed to a giant moat of gators instead of a wall. Seriously?