Up to 80% of seagrasses were lost in Cockburn Sound as a result of poor water quality between the 1960s and 1980s. Since then, water quality conditions have improved considerably, yet seagrass decline has continued in some areas within Cockburn Sound and in neighbouring Warnbro Sound. We visit 25 long-term study sites, measuring shoot density and canopy height in permanent quadrats. The project provides a detailed picture of the health of seagrasses in Cockburn Sound, and is directly incorporated into the annual ‘State of Cockburn Sound’ reports that inform the Minister for Environment, Parliament, the Environmental Protection Authority and the wider public on whether the environmental values and objectives established for the Sound are being met.