Jeff Gaeckle just shared these links to their newly published annual Puget Sound monitoring report. It is not satellite imagery based, but rather uses underwater videography.
Report: Puget Sound Seagrass Monitoring Report (2018-2020)
Data Viewer: Puget Sound Eelgrass Monitoring Data Viewer (2000-2020)
Story Map: Seagrass Monitoring in Puget Sound (2000-2020)
Blog: Ear to the Ground
You can reach Jeff at jeffrey.gaeckle@dnr.wa.gov