Just inside the seawall lie a series of shallow, brackish lagoons connected to the sea through a system of sluices and tidal flaps. The salinity in these lagoons varies widely, but is generally lower than seawater. This specialised habitat supports its own distinctive plants and animals, some of which are only found in this environment.
The lagoons are some of the most important in Britain with populations of rare species including Foxtail Stonewort, Lagoon Shrimp and starlet Sea-anemone.
In winter the flooded lagoons are home to wildfowl such as Mallard, Shoveler and Teal. Spring and autumn bring migrant wading birds including Whimbrel, Curlew Sandpiper and Little Stint.
The islands within Normandy Lagoon enable Little Tern, Ringed Plover and Oystercatcher to breed in relative safety.
The mosaic of ponds, ditches, and lagoons on the reserve support a large number of wetland plants and animals. In winter wading birds including Black-tailed Godwit, Curlew and Lapwing feed in the flooded pastures alongside Wigeon and Brent Geese. Spring sees the arrival of migrants from the south. Wheatears appear on the shingle at Iley Point and Whitethroats sing from clumps of bramble along the Ancient Highway. In early summer look out for Linnets and Stonechats perched on Gorse bushes around the reserve.
Plants flowering on the seawall include Sea Pink, Rock Samphire and Sea Campion. In late summer the ditches are full of the purple-flowered Sea Aster, often attracting Wall Brown and Painted Lady butterflies. Several species of dragonfly patrol the waterways catching insects or searching for a mate. Mammals too make a home on the reserve, Roe Deer and Hares are frequently seen around Normandy Marsh while numerous mice and voles provide food for hunting Barn Owls.