||Marine Sandcastle worms, Phragmatopoma californica, are tube-building sabellariid polychaetes that inhabit the western coast of North American. Sabellariidae have major impacts on the geology and ecology of shorelines. Individual worms build protective tubular shelters by gluing together mineralized materials with a proteinaceous adhesive. The adhesive is the product of at least four distinct secretory cell types, the contents of which are co-secreted from the building organ during tube construction. Prominent hetereogeneous granules contain dense subgranules of Mg and two polyacidic (polyphospho)proteins Pc3A and B, as well as at least two polybasic proteins, Pc1 and Pc4. Equally prominent homogeneous granules comprise at least two polybasic proteins, Pc2 and Pc5, and a sulfated polysaccharide. These distinct sets of oppositely charged components are segregated and packaged into dense secretory granules by electrostatic condensation. Both types of adhesive granules contain latent catechol oxidase, pre-primed with oxygen in the active site. After secretion, activated catechol oxidase ensures rapid and spatially homogeneous oxidative crosslinking of L-DOPA of Pc 1 and 2 proteins with limited mixing of the preassembled adhesive packets. Environmental pH changes also rapidly solidify of multipart polyelectrolytic of sandcastle worm adhesive due to formation of polyphosphoprotein Pc3 and Mg complex. The end result is tough and resilient underwater bonds formed with an energy-dissipating, water-filled adhesive foam. The natural adhesive has been a valuable model for development of synthetic adhesives for underwater bonding applications, including medical adhesives.