In 2009 Iran sent an aid ship which was intercepted and denied access to Gaza; a Lebanese ship was also stopped, although blood donations it was carrying were transferred to Gaza.
I don’t see why a ship of the Iranian Red Crescent would need to be allowed passage to Gaza. Although it is a humanitarian organization, it is a national organization of a hostile country. Its not the ICRC. And as the quote above shows, there is already precedent for stopping similar shipments.
A scary possibility is if Iran puts Revolutionary Guards aboard its Red Crescent ships. Just yesterday, Iran’s top leader offered to send Revolutionary Guard ships as protection to other blockade running flotillas. That offer wasn’t very credible. But if Revolutionary Guard troops are aboard the Red Crescent ships to repel any Israeli boarders… it could be very bad.