Marsh/ open water
Total area in Lincolnshire: unknown
Total area within Critical Natural Asset & Basic Natural Stock and selected major Water Feature Sites (approx.): 80ha in 10 sites.

Water courses (such as the Delph Drains), lakes (such as Starmer's Pit), large ponds (such as Blue Lagoon) and their associated aquatic habitats are notable features of Lincoln's "downhill" landscape. Originally Lincoln possessed a great wealth of fenland habitat, for example on the Pyewipe and Washingborough Fens; apart from fragments in sites such as the Witham Marshes this habitat has now largely vanished. Gravel and ballast pits (such as the Trust's Boultham Mere reserve) are a vital element in redressing the loss of ancient wetlands through careful restoration and aftercare schemes.