INTERVIEW: Maritime Historian on how Yemen's Houthi rebels are affecting international shipping

Yemen's Houthis say they have struck four ships in the Red, Arabian and Mediterranean Seas, as well as one in the Indian Ocean overnight as strikes on merchant vessels become more frequent. Yesterday the US military said it destroyed three Houthi uncrewed surface vessels in just 24 hours as part of what it calls "self-defence engagement" in the Red Sea . It comes as the Iran-backed militia in Yemen are boasting their new Unmanned Surface Vessel capability is making it possible to disrupt sea lanes like never before. It's claimed the boats are initially manned, then controlled remotely and can carry up to a 1500kg warhead. Experts say they present yet another significant challange to maintaining shipping through the Red Sea. SBS's Gary Cox spoke to Maritime Historian from Campbell University and the host of 'What's Going On with Shipping' on Youtube, Sal Mercogliano.