USS Rexburg (EPCE(R)-855) was built as a PCE(R)-848-class rescue escort patrol craft for the United States Navy during World War II.

After working through the 1950s and 60s as an oceanographic research vessel for the Navy Electronics Laboratory, Rexburg was decommissioned in 1970 and sold to the Church of Scientology as MV Excaliber.

[1] After completing shakedown training in the Gulf of Mexico in January 1945, the unnamed PCE(R)-855 transited the Panama Canal to join the Pacific Fleet.

On 7 June 1946 she was redesignated EPCER-855 and underwent alterations at Long Beach Naval Shipyard that enhanced her suitability for service as a laboratory research ship.

[2] Aft armament was replaced by a large cargo boom for towing instruments such as a thermistor chain to determine ocean temperature and salinity gradients from the surface to a depth of 800 ft (240 m).