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Keyhaven Marshes & the Keyhaven River Foreshore

Access, ownership and the legal status of the shoreline below the high-tide mark

1. What the site is

The Keyhaven river, marshes and foreshore sit within the Hurst Castle and Lymington River Estuary Site of Special Scientific Interest (SSSI), notified in 1986 and covering roughly 1,077 hectares of coastal habitat along the north-western shore of the Solent.

The same ground carries several overlapping designations:

SSSI (biological & geological) — Hurst Castle and Lymington River Estuary
SPA (Special Protection Area) — Solent and Southampton Water
Ramsar site — Solent and Southampton Water
SAC (Special Area of Conservation) — Solent Maritime / Solent and Isle of Wight Lagoons
On the seaward side of the sea wall, the SSSI comprises intertidal mudflats, Spartina saltmarsh and higher-level saltmarsh, with Hurst Spit forming the south-western boundary. This intertidal zone is not incidental to the designation — it is the notified feature itself.

2. Who owns and manages it

The Lymington and Keyhaven Marshes reserve (c. 738 ha) is leased by the Hampshire and Isle of Wight Wildlife Trust, which manages it to protect the coastal habitat. Hampshire County Council owns and manages the adjoining Local Nature Reserve and the sea-wall footpath network from which the marshes are viewed.

The Trust's own visitor guidance is explicit: there is no public access onto the marsh itself. Visitors are asked to keep to the sea-wall path and view the reserve from there, both to avoid disturbing nesting and wintering birds and because the intertidal mud and saltmarsh are physically hazardous — soft mud and fast tidal channels.

3. The legal position on swimming/bathing below high water

English law generally recognises a public right to navigate and bathe in tidal waters below the mean high water mark, even where the foreshore itself is privately owned. This right is well established around most of the Solent coast — sea swimming is common and unrestricted a short distance away at Milford-on-Sea, Barton-on-Sea and Calshot.

Keyhaven Marshes is the exception to that general picture, for two separate reasons that reinforce each other:

Leasehold control: the Wildlife Trust holds a lease over the foreshore/marsh and can restrict entry onto that land as a matter of ordinary land management and trespass law.
SSSI status: because the intertidal mudflat and saltmarsh are themselves the notified habitat, damaging or disturbing them can risk an offence under the Wildlife and Countryside Act 1981, independent of any trespass question.
Natural England's own England Coast Path planning for this stretch (Highcliffe to Calshot) confirms the same logic: the proposed trail is deliberately routed inland around this section specifically "to take the trail away from areas of nature conservation interest and avoid unsuitable saltmarsh and flats" — i.e. the statutory conservation body treats the marsh/mudflat as an area from which general public access should be steered away, not merely discouraged informally.

4. Practical summary

Question
Position
Can I walk onto the marsh/mudflat?
No — no public access; stay on the sea-wall path.
Can I swim below high water here?
Not sanctioned by the Trust; the intertidal zone is the protected habitat itself, and entry is restricted/discouraged on conservation and safety grounds.
Is this the same everywhere on the Solent?
No — swimming is normal and unrestricted nearby (Milford, Barton, Calshot); Keyhaven is a specific, designated exception.
What is the legal basis for restriction?
Trust leasehold/land management, reinforced by SSSI protection (Wildlife and Countryside Act 1981) and Natural England's own access routing.
Sources

Hampshire & Isle of Wight Wildlife Trust (Lymington & Keyhaven Marshes reserve page); Hampshire County Council (Lymington & Keyhaven Marshes LNR page); Natural England, Designated Sites View — Hurst Castle and Lymington River Estuary SSSI; Natural England, England Coast Path: Highcliffe to Calshot — Natural England's Proposals (Ch. 3).