The newly formed Chicxulub crater was rapidly filled by seawater then disturbed by tsunami and seiche waves. Sedimentary layers deposited as wave energy declined provide a unique window into the environment of the nascent crater in the months and years to millennia after the impact. Geochemical data show temperatures in hotter regions of the crater in excess of 70°C for the first few years with heat derived from the underlying melt sheet via hydrothermal circulation. Cooler regions of the crater became habitats soon after impact with a suite of fossils indicating diverse life on the seafloor and sea surface, ranging from microbes to marine arthropods, and possibly fish. We suggest that this community was sustained by nutrients and heat from the hydrothermal system. The rapid early recovery in the Chicxulub crater and ocean above demonstrates the resiliency of life under extraordinarily harsh conditions, which has important ramifications for early life on Earth and life on other planets.