Would you give a swarm type attack a chance in the restricted waters of the Gulf? There was this article about “rule breaking warfare” and this computer geek kept on winning a naval simulation because he would build a fleet of “dingies” and just overwhelm the more traditional fleets with numbers. What would happen in Iran sent out say 1,000 speed boats packed with explosives on a kamikaze mission against a US task force in the Gulf? It might just take 1% to get through and a US carrier is at the bottom of the gulf.
I think that your "1%" or more would probably wreck each other in the effort to find a carrier strike group to attack. These carriers don't just go around broadcasting their location for all to know. And if Iran did gather 1000 boats in one location they'd be detected by satellite/Global Hawk/Predator UAV in plenty of time to be destroyed in port.