[abstFig src='/00280001/09.jpg' width=""300"" text='Virtual Mooring Buoy ""ABA""' ]We developed a virtual mooring buoy, called an autonomous buoy “ABA” for AUV, which navigates the sea using thrusters in 2014. Its purpose was to deploy autonomous underwater vehicles (AUVs) effectively in seafloor exploration. The ABA tracks and positions AUVs operating underwater using onboard acoustic positioning. We have deployed the ABA with two type AUVs in seafloor exploration. That conducted in February 2015 used the ABA with one AUV to survey and inventory mineral deposits, demonstrating the ABA’s capability of positioning an AUV navigating at 1,370–1,550 m depths at a standard deviation of 100 m or less and tracking it while maintaining a horizontal distance of 50 m or less. The ABA navigated the AUV within a position error of about 10 m.