KVH Industries TracPhone FB250 Installation Manual page 136

C.3.6 RF Ground (Capacitive)
Underwater ground potential that is capacitively coupled to seawater ground.
Typically numerous pieces of bonded underwater metal parts such as keel
(isolated), water tank, engine block etc. will act as a capacitive RF ground (that
is; no DC connection to seawater). Often referred to as "counterpoise" for the
SSB/HF aerial system.
C.3.7 RF Ground (Electrical)
Underwater ground potential that is electrically coupled to seawater ground
by means of a separate ground plate (e.g. Dynaplate). Also referred to as
"counterpoise" for the SSB/HF aerial system.
Appendix C: Grounding and RF protection
General about marine grounding 123