Houthi bomb boats, including some not seen before, are threatening Red Sea ships while the US Navy's aircraft carriers are away

• The Houthis have stepped up their attacks and intimidation efforts with their drone boats.
• In their latest messaging, the rebels shared a new video of a previously unseen system in action.
• The uptick comes as the US Navy lacks an aircraft carrier in the region.

The US Navy is in the middle of changing up its forces in the Middle East. An aircraft carrier that spent months in the counter-Houthi fight heads home, leaving a gap as another one makes its way toward the region to take over.

It has been over a week since the US last had an aircraft carrier on station in the Red Sea, meaning the Pentagon can't depend on the routine combat air patrols and immense firepower having a carrier in the region has provided over the past seven months.

The Houthis have been stepping up drone boat operations, employing small watercraft that can be packed with explosives and detonate on impact. These weapons can be used to strike merchant vessels and cause catastrophic damage, which has already been the case in at least one instance in recent weeks.

Drone boats are not a new capability for the Houthis. They have employed them in years past and throughout their ongoing campaign of attacks on merchant vessels and commercial shipping lanes.

During the first few months of the year, US airstrikes in Yemen destroyed the drone boats nearly every time the Houthis tried to send them into the water. But in June, the Iran-backed rebels managed to launch well over a dozen crafts — far more than they had in any previous month. Last month, one of the Houthi drone boats struck a commercial vessel, the MV Tutor, for the first time since the campaign began in November.

In the June 12 attack, the Houthis used a small, slow-moving boat staffed with two dummies, appearing to disguise the crude-looking weapon as a common fishing craft. Hours after the initial strike, the rebels hit the Tutor with a missile, causing it to later sink.

More than a week after the Tutor attack, on June 22, the Dwight D. Eisenhower Carrier Strike Group, which spent more than seven months battling the Houthis, finally left the region to head home, bringing with it the carrier Ike and dozens of fighter aircraft.

The Ike's eventual replacement — the Theodore Roosevelt Carrier Strike Group — won't arrive for some time. And in the meantime, the Houthis appear to be taking advantage of the decreased US Navy air patrols and employing more drone boats.

United Kingdom Maritime Trade Operations, an element of the British Royal Navy, has reported multiple incidents over the past few days that appear consistent with such attacks.

On June 27, for instance, UKMTO cited one threat as a "waterborne improvised explosive device," and on June 30, it said a merchant vessel was approached by "a mixture of fast boats and smaller kayak-type boats," adding that "some were observed as uncrewed."

On June 30, the Houthi rebels revealed what they said is a highly advanced drone boat that can travel at speeds of 45 nautical mph and deliver an explosive payload of up to 3,300 pounds. The group claimed to have used the drone boat in a June 23 attack on the MV Transworld Navigator and published footage purporting to show the unmanned craft strike the much larger merchant vessel.

Business Insider was unable to immediately verify the Houthi claim. US Central Command said at the time that the Transworld Navigator was hit by a "suspected uncrewed aerial system" and did not mention a drone boat.

In the June 30 video, the Houthis also showed the drone boat going through various maneuvers and training exercises. At one point, rebels can be seen manually operating the craft before they dive off the side into the water and allow it to be remotely piloted.

The newly revealed drone boat is far more sophisticated-looking than the one that struck the Tutor and appears notably larger than unmanned crafts that the rebels publicized and tested earlier in June, underscoring the different capabilities that the Houthis have in their arsenal.

Experts have said that the uptick in drone boat attacks and the Houthis' newfound success in striking commercial vessels with such weapons indicates that they're learning from their many months of attacks and are able to adjust their operations accordingly.