For many years the lakes known as broads were regarded as natural features of the landscape. It was only in the 1960s that Dr Joyce Lambert proved that they were artificial features, that they were flooded medieval peat excavations. In the Middle Ages the local monasteries began to excavate the peatlands as a turbary business, selling fuel to Norwich and Great Yarmouth. Norwich Cathedral took 320,000 tonnes of peat a year. Then the sea levels began to rise, and the pits began to flood. Despite the construction of windpumps and dykes, the flooding continued and resulted in the typical Broads landscape of today, with its reedbeds, grazing marshes and wet woodland.
Various attempts were made to extend the navigable rivers. The longest-lasting was on the River Waveney, where an Act of Parliament passed on 17 March 1670 authorised improvements which included three locks, at Geldeston, Ellingham and Wainford. The head of navigation became a new staithe at Bungay. The new section was a private navigation which was not controlled by the Yarmouth Haven and Pier Commissioners, who had responsibility for the rest of the Broadland rivers. It remained in use until 1934 and, although the upper two locks have been replaced by sluices and Geldeston lock is derelict, the Environment Agency have negotiated with local landowners to allow use by canoes and unpowered vessels which can be portaged around the locks.
The next attempt was to extend navigation on the River Bure from Coltishall to Aylsham, which was authorised by an Act of Parliament on 7 April 1773. Five locks were built, to bypass mills, at Coltishall, Oxnead Lamas, Oxnead, Burgh and Aylsham. There were financial difficulties during construction, but the works were eventually completed and opened in October 1779. At Aylsham, a 1-mile (1.6 km) cut was made from the river to a terminal basin, where several warehouses were constructed. Despite the arrival of the railways in 1879, goods continued to be carried to Aylsham by wherries until 1912, when major flooding badly damaged the locks. Unable to fund repairs, the Commissioners closed the 9-mile (14 km) section above Coltishall, although it was not formally abandoned until 1928. All of the locks are derelict, but the course can still be used by canoes and light craft, which can be portaged around the locks.
The third attempt was to make the River Ant navigable from Dilham to Antingham. An Act of Parliament was obtained on 5 May 1812, which authorised the North Walsham & Dilham Canal, but work on its construction did not start until April 1825. The canal was a true canal, as its route did not use the bed of the river, and its construction, including six locks, was completed in 1826. It was about 8 3⁄4 miles (14.1 km) long, and the locks raised the level by 58 feet (18 m). In 1886 the canal was sold to a miller called Edward Press for £600, but the principal clerk absconded with most of the money and it was never recovered. In 1893 the section from Swafield locks to Antingham was abandoned, and the lower section was damaged by flooding in 1912. Some attempts were made to improve it in the 1920s, but the last commercial traffic used it in 1934, and it gradually became derelict after that. There is still a public right of navigation to Swafield, and there is a campaign to reopen it.
In 1814 the merchants of Norwich first suggested a plan to improve the route between Norwich and the North Sea, as the shallowness of Breydon Water created difficulties for trading vessels, and there was organised theft of cargo during its transshipment at Great Yarmouth, for which 18 men were convicted of taking the goods and one of receiving it in 1820. The initial plan was to dredge a deeper channel along the southern edge of Breydon Water, but the scheme was opposed by the people of Yarmouth. A more expensive scheme, involving the construction of a new cut to link the River Yare to the River Waveney, together with a channel between Oulton Broad and Lake Lothing, where a sea lock was needed, was also opposed by Yarmouth, but formed the basis of a Bill to Parliament. An Act of Parliament was passed on 28 May 1827, creating the Norwich and Lowestoft Navigation Company, and the work of construction and dredging of the River Yare and the Oulton Dyke was completed in 1833. The initial capital of £100,000 was inadequate and a further £50,000 was borrowed from the Exchequer Bill Loan Commission. The venture was not a commercial success, and, with expenditure exceeding income, the Company was unable to repay its loan. The Haddiscoe Cut was taken over by the Commissioners in 1842 and sold to the railway developer Sir Samuel Morton Peto.
The Broads have been a boating holiday destination since the late 19th century. In 1878 small yachts were available to hire from John Loynes, and with easy access to the area by rail from London, Harry Blake created an agency for yachting holidays in 1908. The first boats were owned by the boatbuilder Ernest Collins of Wroxham, but other boatyards were soon added to the business. The range of boats expanded to include powered cruisers in the 1930s, and the Hoseasons agency was founded soon after the Second World War. By the 1980s the number of cruisers available for hire was 2,400, but had decreased to around 1,700 by 2004. For conservation reasons there is a strict speed limit enforced on all vessels, to reduce waves eroding the riverbanks. These speed limits are hardwired onto most rental vessels.