The article focuses on human-occupied vehicle (HOV) Alvin is midway through the final phase of an overhaul that will allow the submersible to dive to 6,500 meters. Topics include the increased depth range will give ocean scientists the ability to explore 99% of the ocean floor and study the abyssal region, and the least-understood areas of the deep sea and home to high-temperature hydrothermal vents, submarine volcanoes, subduction trenches, mineral resources, and more.