In sailing and boating, freeboard means the distance from the waterline to the upper deck level, measured at the lowest point of sheer where water can enter the boat or ship. In commercial vessels, the latter criteria measured relative to the Ship's load line, regardless of deck arrangements is the mandated and regulated meaning.

In yachts, a low freeboard is often found on racing boats, for weight reduction and therefore increased speed. A higher freeboard will give more room in the cabin, but will increase weight and may compromise speed. A higher freeboard also helps weather waves and reduce the likelihood of green seas on the weather deck. A low freeboard boat is susceptible to swamping in rough seas. Freighter ships and warships use high-freeboard designs to increase internal volume which also allows them to satisfy IMO damage stability regulations due to increased reserved buoyancy.

1. Nautical.

Samuel Plimsoll (10 February 1824 – 3 June 1898) was a British politician and social reformer, now best remembered for having devised the Plimsoll line (a line on a ship's hull indicating the maximum safe draft, and therefore the minimum freeboard for the vessel in various operating conditions).

Samuel Plimsoll was born in Bristol and soon moved to Whiteley Wood Hall, Sheffield, also spending part of his childhood in Penrith, Cumberland. Leaving school at an early age, he became a clerk at Rawson's Brewery, and rose to be manager.

In 1853 he attempted to become a coal merchant in London. He failed and was reduced to destitution. He himself told how for a time he lived in a common lodging for seven shillings and two pence a week.

Through this experience, he learnt to sympathise with the struggles of the poor, and when his good fortune returned, he resolved to devote his time to improving their condition.

His efforts were directed especially against what were known as "coffin ships": unseaworthy and overloaded vessels, often heavily insured, in which unscrupulous owners risked the lives of their crews.