The Anthropocene has fundamentally disrupted the relationships between human societies and ecosystems across the planet, transforming natural ecological cycles into environmental and economic crises. In the Mediterranean basin, this disruption materializes along coastlines in the seasonal accumulation of beach-cast Posidonia oceanica: a seagrass endemic to the Mediterranean Sea whose banquettes are routinely removed and landfilled to preserve tourism-driven aesthetic standards, at significant ecological and economic cost. Reframed through the lens of More-than-Human Design and New Materialism, this research approaches this marine residue not as an environmental burden but as an active material agent: a localized, renewable, and structurally potent resource capable of participating in regenerative design processes.