freeboard

plural freeboards

1. nauticalThe vertical distance between the waterline and the uppermost watertight deck of a vessel, or the vertical distance from the waterline up to the top of the gunwale (of an open boat).

   By the time the whole team and all its equipment were loaded on board, there wasn't much freeboard anymore, and if the weather had been worse we might have had to postpone the trip.

   1 more example

   Fortunately the seas was very calm, because the boat’s heavy loading did not give it much freeboard, the gunwale at times being just a couple of inches clear of the water.

   1961, Tom Mead, Killers of Eden, Sydney: Angus and Robertson, page 65

2. The distance between a water level and the top of something that contains or restrains it (such as a dam).
3. The distance between the top of sea ice and the water level.

plural freeboards

1. A type of skateboard which simulates the movement of a snowboard when used on a downhill course, allowing snowboarding techniques, which has an addition of two centerline casters that extend below the traditional skateboard wheels and bogies.