Speaking to a young naval man who travels through that "hot spot", tells me they lock down when going through there as they are not allowed to engage the pirates. The rubber dinghies are not detectable on radar. They run a cable across in front of the ship to which the dinghies are attached on each side. As the ship moves forward it draws the dinghies to the sides of the vessel.
Cunning so and so's. Though they do end up getting their just rewards sometimes. I just read that some of the pirates who hijacked the Saudi tanker drowned as they were escaping with some of the ranson money.