To where? Will illegals raft through the Gulf of Mexico and come ashore or what?
Some of them (though not rafts). "Coyotes" will simply shift from trucks and vans to boats. A lot if them will simply fly to Canada and cross the northern border (if they are paying coyotes hundreds and in some cases thousands of dollars, they can certainly afford a plane ticket to Canada).
NEVER underestimate human ingenuity.