Israel says the blockade prevents weapons from reaching Hamas, while flotilla participants maintain they are civilian aid workers and say international law protects their deliveries. Israeli naval forces detained more than 400 international activists Thursday who were taking part in a flotilla carrying humanitarian aid. Now, a Chicago organization is showing solidarity, by hosting a flotilla of its own on the Chicago River. The Chicago River flotilla is set to launch near State Street on Thursday. While flotilla members say they are a civilian group, international law protects them from delivering humanitarian aid through this channel.