The Hunga Tonga Hunga Ha'apai submarine volcano has experienced repeated erup-tions in the latest decades.The recent one,in January 2022,released an enormous amount of energy in-ducing global perturbations,as tsunamis and atmospheric waves.The structure of the volcano is poor-ly understood,especially its internal structure.Deep-seated magmatic connections are difficult to de-fine or visualize.We use a high-resolution gravity data set obtained via satellite to calculate the Bougu-er anomaly over its structure,to perform a preliminary exploration of its interior.Executing 3D gravi-ty inversions,we find a complex plumbing system with various exhaust trajectories and multiple sur-face pockets of low-density material within the volcanic edifice;some appear to be associated with ring fractures.This is in line with the report of the 2009 eruption,described as beginning from multiple vents.We found no signs of a magma chamber within 6 km depth,although several volcanic conduits are identified from such depth to the surface.Density variations occur within a plumbing conduit or may vary from one conduit to another in the same volcano.These models yield quantitative estimates for areas of magma-water interaction,constituting a baseline to compare with structural changes to be induced in future eruptions.