Put a moat filled with alligators in front of the wall.
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If the wall was built on the actual Texas/Mexico border line you’d have water as the
middle of the Rio Grande river is the border in most locations.
“...the middle of the Rio Grande river is the border in most locations.”
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I hadn’t thought of that!
Build the wall on the Mexican side; the Rio Grande is then 100% in Texas.
Or build hundreds of high-speed cigarette boats and have them patrol the Rio Grande 24/7.