The recorder transmits acoustic signals to the buoy, which, in turn, relays the measurements of wave height to satellites.
From the newsweek.com
It has a $1.7 million Navy contract to use a buoy to power an underwater acoustic detection system on the edge of the continental shelf off New Jersey.
From the inrich.com
Winsor and Seitz suspended acoustic tags, usually implanted in fish, at different depths along a buoy line near Juneau.
From the sciencedaily.com
An acoustic link transmits data from the bottom pressure sensor to the surface buoy, and then satellite links relay the data to NOAA tsunami warning centers.