The seafloor beneath our oceans is not just barren rock—it hosts dynamic systems where seawater circulates through cracks and faults in the Earth's crust. This process, known as hydrothermal circulation, helps cool the ocean floor, moves chemicals through the Earth, and supports rare ecosystems with unique species. However, very few of these systems have been directly studied.

In this study, we explored two underwater hills—Caballito Knoll and La Pulperia Hill—off the coast of Costa Rica. By measuring how much heat moves through the seafloor and using underwater robots to observe the area, we found signs that warm fluids are moving under the sediments between the two hills. One hill seems to pull water in, while the other releases it, possibly forming a natural 'siphon.' This warm outflow also supports marine life like the deep-sea octopus Muusoctopus, which was seen brooding near the warm vents.

These findings help scientists understand how these hidden systems work and consider widespread they might be. However, they are also fragile. While Costa Rica has protected this area from industrial disturbance, many other similar sites in the deep sea remain unexplored and vulnerable to activities like deep-sea mining.