An undersea antineutrino observatory being developed in Hawaii presents excellent potential for neutrino science. The observatory is a 10-kT monolithic, scintillating organic liquid detector for deployment in the deep ocean. Its design allows for relocation from one site to another. Positioning the observatory 50-60 km distant from a nuclear reactor complex enables precision measurement of neutrino mixing parameters Δm221, θ12, and, for non-zero θ13, Δm231 and Δm232, possibly leading to determination of neutrino mass hierarchy. At a mid-Pacific location the observatory can measure the flux of neutrinos from the decay series of uranium and thorium primarily in earth's mantle, and performs a sensitive search for a hypothetical natural fission reactor in earth's core. Subsequent deployments at other mid-ocean locations would test lateral heterogeneity of uranium and thorium in earth's mantle. Sites with depth greater than ∼ 5 km allow a relatively background-free measurement of pep and CNO solar neutrinos, probing the energy region marking the transition between matter- and vacuum-dominated oscillations. The observatory provides sensitivity to galactic supernova neutrinos and their potential to reveal neutrino mass hierarchy, and to the diffuse supernova neutrino background. Initial engineering and design studies for this project are complete, an international collaboration of physicists and geologists continues to grow, and a demonstration deployment is in progress.