New Zealand straddles the converging tectonic boundary between the Pacific Plate and Australian Plate. This convergence is expressed as the Hikurangi Subduction Zone in the north and the incipient Puysegur Trench in the south. The two subduction zones are connected by the continental scale Alpine Fault and have opposite polarities, with the Pacific Plate slipping beneath the Australian in the north and the Australian Plate slipping beneath the Pacific in the south. What is the structure of this unique plate configuration at depth, and how does the upper mantle accommodate this transition? We attempt to answer these questions by studying the seismic velocity structure of the lithospheric mantle. An amphibious dataset using recordings from both land and ocean-bottom seismometers increases the spatial extent we investigate over this tectonic boundary. Using the teleseismic two-station phase-velocity dispersion method in a Bayesian framework, we produce probabilistic path-averaged 1D shear wave velocity curves between station pairs. These 1D velocity models are then used in a tomographic inversion to produce maps of shear wave velocity that encompass the upper mantle beneath the entirety of New Zealand. We observe the interaction of velocity structures associated with the down-going Pacific Plate, the Alpine Fault and the Taupō Volcanic Zone.