Note that the 5492CPM reading mentioned above is due to sensor failure because of water infiltration. The sensor was repaired and reinstalled in September 2017. This sensor page is kept for historical purposes, the new sensor ID is 20105 and is available here.
This Seawater Probe calibration is 960 CPM per µSv/hr. Geiger tube is the LND 78017.
Note that CPM readings will be higher relative to North American terrestrial sensors, as the tube used for this Seawater probe is more sensitive than most.