Designed to move across water, ships sink when they are unable to perform their anthropogenic function; in other words, when they fail as watertight works of nautical architecture. Yet the topside cycles of repair and refitting do not end even as the wrecked ship is absorbed into the underwater environment. Marine colonizers repurpose the structure according to their own designs, in a process of ‘naufragic architecture’, that produces an animate, corporeal machine (in Levi Bryant’s terms). This extrahuman, machinic architecture confuses UNESCO's domains of ‘natural’ and ‘cultural’ heritage. Further, while viewing underwater heritage as a mere ‘resource’ commodifies the site for potential human extraction, learning how the site itself works for or against the generation of biodiverse ecosystems would lead to more productive archaeological interactions. Naufragic architecture depends on the toxicity of construction materials, cargo, and surrounding seafloor, so as works-in-progress, shipwrecks should be considered sources—of contamination, biodiversity, nutrients, knowledge—rather than merely resources.