Tidal island

A tidal island is a raised area of land within a waterbody, which is connected to the larger mainland by a natural isthmus or man-made causeway that is exposed at low tide and submerged at high tide, causing the land to switch between being a promontory/peninsula and an island depending on tidal conditions.

Because of the mystique surrounding tidal islands, many of them have been sites of religious worship, such as Mont-Saint-Michel with its Benedictine abbey.

Tidal islands are also commonly the sites of fortresses because of the natural barrier created by the tidal channel.

Grótta in Seltjarnarnes, the Capital Region 43 (unbridged) tidal islands can be walked to from the UK mainland.

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Diagram of tidal island at low tide and high tide
St Michael's Mount , Cornwall , at high tide, c. 1900
Cramond Island , Scotland , at high tide: the causeway is submerged, but the anti-boat pylons are still visible
Mont Saint-Michel in Normandy
Rough Island opposite Rockcliffe, Dumfries & Galloway , Scotland
Worm's Head at the end of Gower , Wales
Gunns Island, connected to Ballyhornan Bay, Northern Ireland at low tide
Bar Island in Maine , U.S.
Rangitoto Island forms a backdrop to a wave-cut platform off Achilles Point , Auckland, New Zealand.