Bass shoal (Rohan Holt at CloudBase Productions Ltd)

Large shallow inlets & bays

The large shallow inlets and bays feature comprises the embayment of St Brides Bay, the marine inlet (or ria) of the Milford Haven waterway and peripheral embayments including: Whitesands Bay; South Haven, Skomer; Gateholm – West Dale bays; Freshwater West.

St Brides Bay seabed generally slopes gradually westwards from the sediment flats at its eastern shore. Depth in the outer parts of the bay reaches 50m. The Bay has a wide range of different sediment types that support many species including long-lived animals buried within and living on the sediment surface.

The shallow inlet which is the outer section of the Milford Haven waterway contains species of particular interest – seagrass and maerl and seagrass. Maerl is a chalky red seaweed that interlocks to form a loose lattice structure which provides a useful place to live for other species. Maerl beds are present along the north side of the waterway. Seagrass is the only subtidal British marine flowering plant and is rare in Wales.

Seagrass plants form meadows which stabilise the sediment and provide shelter for fish. The largest naturally occurring areas of seagrass within the SAC are found at North Haven, Skomer Island and Littlewick Bay within the Milford Haven waterway.

In 2020 the UK’s first full scale seagrass restoration trial took place just off Dale. Over one million seeds were planted in a 2-hectare area. Further detail on this is on the projects page.

A voluntary agreement is in place within the Milford Haven waterway to protect the seagrass and maerl beds from anchoring and mooring activity. To read more about these sensitive habitat protection zones, see the marine code information on the projects page.