The Kaiyō No. 1-class oceanographic research ship (第一海洋型海洋観測船,, Daiichi Kaiyō-gata Kaiyō-kansokusen) was a class of oceanographic research ship/weather ship of the Imperial Japanese Navy (IJN), serving during World War II. The IJN official designation was 200-ton oceanographic research ship (二〇〇瓲海洋観測船,, 200-ton Kaiyō-kansokusen).
Construction
In 1938, the IJN wanted to investigate the weather and ocean currents in a potential future battlefield. Kaiyō No. 1-class ships were built for the purpose. The IJN made Hokkaido Fisheries Research Institute San'yō Maru a sample for the Kaiyō No. 1. All ships were deployed in the Hydrographic Department, and they were directly controlled by the Naval Ministry. Therefore, being government ships, they raised civil ensign, not the naval ensign. The crew were civil servants except for several warrant officers.
Survived war at Uraga;[8] transferred to Ministry of Transport on 29 November 1945; transferred to Maritime Safety Agency on 1 May 1948 (hull number HG-01, later HM-01); renamed Kaiyō Maru No. 4 (第四海洋丸,, Daiyon Kaiyō Maru) on 20 October 1949; renamed Kaiyō (海洋) on 15 December 1956; retired on 26 March 1964.
Survived war at Kasaoka;[8] transferred to Ministry of Transport on 29 November 1945; transferred to Maritime Safety Agency on 1 May 1948 (hull number HG-02, later HM-02); renamed Kaiyō Maru No. 5 (第五海洋丸,, Daigo Kaiyō Maru) on 20 October 1949; sunk by jets of water and tephra[9] from the eruption of Myōjin-shō on 24 September 1952; struck on 27 April 1953.