Antarctic Bottom Water (AABW) production supplies the deep limb of the global overturning circulation and ventilates the deep ocean. While the Weddell and Ross Seas are recognised as key sites for AABW production, additional sources have been discovered in coastal polynya regions around East Antarctica, Vincennes Bay being the latest. Vincennes Bay, despite encompassing two distinct polynya regions, is considered the weakest source, producing Dense Shelf Water (DSW) only just dense enough to contribute to the lighter density classes of AABW found offshore. Importantly, the network of local glaciers and upstream Totten Ice Shelf system are all reportedly thinning and the freshwater input from such melting is likely to influence water mass structure. Accordingly, Vincennes Bay presents an interesting test case for DSW/AABW sensitivity to climate-driven changes in Antarctic coastal oceanography. Here we provide the first detailed observations of the Vincennes Bay shelf region and surrounds, using CTD data from instrumented elephant seals in late summer/early fall. We find that Vincennes Bay has East Antarctica’s warmest recorded intrusions of modified Circumpolar Deep Water (mCDW), intrusions that both hinder sea-ice production and contribute salt to new DSW formation. Warm mCDW is also observed to be driving basal melt in Vincennes Bay, as seal CTD data provide the first direct observational evidence for inflow of basal melt to this region. As the most marginal of AABW sources, Vincennes Bay is a particularly useful region for assessment of the sensitivity of AABW production to changes in climate.