freeboard
noun
free·board ˈfrē-ˌbȯrd 
1
: the distance between the waterline and the main deck or weather deck of a ship or between the level of the water and the upper edge of the side of a small boat
2
: the height above the recorded high-water mark of a structure (such as a dam) associated with the water
Example Sentences
Recent Examples on the Web Only a few small inches of freeboard lay between the water and the top of my gunwales. 
Florence Williams, Outside Online, 1 Feb. 2022 New Jersey and New York instituted two feet of freeboard after Superstorm Sandy. Alex Harris, sun-sentinel.com, 2 Dec. 2019 The Yamaha doesn't appear to have any flair up front to knock down spray, and at the bow the freeboard (the distance from the edge of the boat down to the deck) is minimal. Ezra Dyer, Popular Mechanics, 11 July 2019 The present system is overdesigned for those surges, with earthen levees and concrete structures containing as much as 3 feet of extra storage space, or freeboard, to account for subsidence and sea level rise over their 50-year design life. Mark Schleifstein, NOLA.com, 22 May 2018 And maybe a 1-foot freeboard isn't high enough, Berginnis said. Thom Patterson, CNN, 31 Aug. 2017 Or consider Nashville, Tennessee, which has a freeboard of 4 feet. Thom Patterson, CNN, 31 Aug. 2017 Much of Houston has a 1-foot freeboard, Berginnis said. Thom Patterson, CNN, 31 Aug. 2017 See More
Florence Williams, Outside Online, 1 Feb. 2022 New Jersey and New York instituted two feet of freeboard after Superstorm Sandy. Alex Harris, sun-sentinel.com, 2 Dec. 2019 The Yamaha doesn't appear to have any flair up front to knock down spray, and at the bow the freeboard (the distance from the edge of the boat down to the deck) is minimal. Ezra Dyer, Popular Mechanics, 11 July 2019 The present system is overdesigned for those surges, with earthen levees and concrete structures containing as much as 3 feet of extra storage space, or freeboard, to account for subsidence and sea level rise over their 50-year design life. Mark Schleifstein, NOLA.com, 22 May 2018 And maybe a 1-foot freeboard isn't high enough, Berginnis said. Thom Patterson, CNN, 31 Aug. 2017 Or consider Nashville, Tennessee, which has a freeboard of 4 feet. Thom Patterson, CNN, 31 Aug. 2017 Much of Houston has a 1-foot freeboard, Berginnis said. Thom Patterson, CNN, 31 Aug. 2017 See More Word History
First Known Use
1718, in the meaning defined at sense 1