semisubmersible
adjective
semi·sub·mers·ible ˌse-mē-səb-ˈmər-sə-bəl 
ˌse-ˌmī-,
-mi-
: being a floating deepwater drilling platform that is towed to a desired location and then partially flooded for stabilization and usually anchored
semisubmersible noun
Example Sentences
Recent Examples on the Web But capacity wasn’t the point: This was the first time anyone had put a multimegawatt turbine on a semisubmersible platform in the Atlantic Ocean. 
Judith Lewis Mernit, The Atlantic, 4 Nov. 2021 The platform pictured is a semisubmersible production facility, not a drilling platform. New York Times, 8 Jan. 2018 Psubs members have been tracking the development of the drug runners’ semisubmersible creations for years. Jim Popkin, WIRED, 29 Mar. 2011
Judith Lewis Mernit, The Atlantic, 4 Nov. 2021 The platform pictured is a semisubmersible production facility, not a drilling platform. New York Times, 8 Jan. 2018 Psubs members have been tracking the development of the drug runners’ semisubmersible creations for years. Jim Popkin, WIRED, 29 Mar. 2011 Word History
First Known Use
1962, in the meaning defined above