If you can't have big guns on board, and I understand many port facilities have issues with that, I think there's an opportunity to build computer guided catapults. Load them up with 500 pounds of rocks, bananas or manure. Launch it and send these filth down to Davy Jones' locker.
Load them with pig offal in a plastic bag, one which air-bursts and paints the whole target with blood and guts. And advertise what you are doing and will do.