Dozen or so ships would be enough to blockade both Suez and Panama... That would cause substantial damage to global shipping industry... Not even that expensive. Hundred or two hundred million would do...
Panama is not that busy. A much better target would be the kiel canal (Nord- Ostsee Kanal in German), which is the busiest waterway in the world 25000 ships yearly vs 19000 ships for the Suez vs 12000 for Panama.
