The main aim of the study was to identify mechanisms causing degradation of the Puck Lagoon′s primary environment and to suggest some remedial measures and techniques for its restoration, apart from the newly installed sewage treatment plant near Puck. Results of the study demonstrate an excessive seasonal development of filamentous brown algae of the family Ectocarpaceae. This excessive growth on the bottom of the lagoon plays a significant role in eliminating nutrients from the water, limiting the vernal development of plankton, and considerably increasing water transparency, but strongly affecting living conditions of the original benthic macrophytes. In late summer, the brown algae biomass undergoes rapid decomposition and enriches the sediment with organic matter. Sediment analyses revealed no excessive concentration of heavy metals or organic contaminants, their concentrations being usually proportional to the organic matter content. Experimental seeding- of vascular plants and observations on assemblages of sessile fauna and flora indicate that reintroduction of original species and deployment of artificial reefs is feasible and purposeful.