Abstract
<jats:title>Abstract</jats:title> <jats:p>The wrack is the seaweeds and marine debris deposited on the shore at high tide. The wrack is often used by local ordinances to mark where private property ends and public commons begin. This transient zone of oceanic produce is a site of local cultural practices where the open property of the commons is used by coastal communities for food and livestock forage. Ethnophycological studies of the knowledge and practices of gatherers and users of marine macroalgae provide the empirical basis for this philosophical investigation into wrack-based epistemologies and ontologies. Considering the use of gutweed and eelgrass as seasonal markers by the Nuu-Chah-Nulth; the communal care of the seaweed-eating North Ronaldsay sheep; and the legislative use of the wrack line as private–public marker in New England, this chapter examines some ontological struggles that arise when what the wrack is, who it is for, and what boundaries it indicates are in dispute.</jats:p>