A Seattle-based startup, Endurance Energy, has demonstrated what it describes as the first functional subsea geothermal power plant in the Pacific Ocean. The system operated near Axial Seamount, an active underwater volcano approximately one mile below the ocean surface, generating a brief period of net-positive electricity during a September test deployment. The three-week trial involved drilling into the seafloor at a depth exceeding 5,000 feet (1,524 meters) using a subsea lander drill deployed from the vessel Ocean Guardian. Two holes were drilled, with the second being cased and fitted with a valve to create a well. The 100-kilowatt Adélie power plant, designed to vaporize hydrothermal fluid to drive a turbine, was connected to the Regional Cabled Array—a network of undersea fiber-optic and electric cables operated by the University of Washington and funded by the U.S. National Science Foundation. During testing, the plant achieved a peak net output of 16.5 kilowatts and produced 60 watt-hours of electricity over nearly 30 seconds, marking the first instance of a subsea geothermal system producing more power than it consumed. However, the test faced technical setbacks, including insufficient fluid flow from the initial shallow well (2 inches wide, extending 52 feet deep) and a software-triggered shutdown due to a battery module anomaly, followed by an electrical cable failure caused by seawater intrusion. Endurance Energy plans to drill deeper wells (up to 260 feet) in future iterations to improve fluid delivery and scale up operations. The company intends to deploy upgraded systems, including a renamed Gentoo generator, with a target commercial deployment in Tonga in 2027. Tonga, like many Pacific island nations, relies heavily on imported diesel fuel, making renewable alternatives increasingly urgent amid rising fuel costs. Environmental monitoring during the test included water sampling, seafloor biodiversity tracking, and collaboration with independent researchers to assess ecological impacts. While experts note the technical feasibility demonstrated, they caution that cost competitiveness with land-based geothermal or other renewables remains uncertain. Endurance Energy aims to leverage this proof point to advance subsea geothermal development for Pacific Rim nations and other regions with offshore geothermal potential.