Several roads around the world are periodically flooded twice a day by the high tide. The roads flood twice daily with incoming tides and as the tides go out slippery seaweed is left all over it.
To drive on them ask about the tide times. In general, operate the vehicle controls slowly. In case of dense fog, turn on your headlights and your fog lights front and rear (if available). It is also strictly forbidden to park on the pavement. When the roads submerged, the causeways are a slippery stretch indeed and especially treacherous on two wheels.
Each year there are many reports of people 'risking it' and having to be rescued from the roads. Their cars aren't as lucky though and are generally ruined, so the lesson here is don't take risks! Weather conditions may close these roads.
The most interesting periodically flooded roads are:
Located in Gwynedd, in north-west Wales, Shell Island is a peninsula and the largest campsite in the UK. Twice a day, the tidal causeway to the island disappears with the tides, leaving the area out to sea. Located west of Llanbedr, within the Snowdonia National Park, the peninsula, also known as Mochras, is linked by a tidal causeway which is covered by sea water at high tide. The tide flows out through a series of drain pipes. Weather conditions may close causeway. A fee is charged to cross the causeway. The causeway lies across the estuary of the River Artro when the tide is out and is cut off by the tides twice a day, and you really need to be careful with the timing – is dedicated to campers; there are no pitches, and the only rule is to stand 20 meters from each other.
Located in the county of Northumberland, in the extreme Northeast corner of England, just a few miles south of the border with Scotland, it lies a tidal island know as Holy Island, also called Lindisfarne. Twice a day the ancient path to the island disappears with the tides, leaving the Holy Island of Lindisfarne out to sea. Each year there are many reports of people 'risking it' and having to be rescued from one of the raised safety points on the causeway. It’s a historic small island located in the west North Sea, 2 mi (3 km) from the English Northumberland that access is by a paved metalled causeway, called Lindisfarne Causeway, which is covered by the North Sea twice in every 24 hour period. This stunning and remote island is home to Lindisfarne Castle and Priory and is surrounded by breath-taking coastal scenery. It gets 650,000 visitors from all over the world every year.
Passage du Gois (also known as Gôa) is located between Île de Noirmoutier and Beauvoir-sur-Mer, in the department of Vendée, and it’s one of the routes that connects the island to the mainland. The Passage du Gois is an extraordinary location in France and a national monument. The 4,150 meters long causeway is only accessible with the low tide and then only 1 ½ hour before the lowest tide and 1 ½ hour afterwards. The stone paved causeway was first used during the 16th century and is still used daily by tourists and locals. At high tide the road lies under 1.5 - 4 metres of water.
Located in the Danish Wadden Sea islands off the southwest coast of Jutland, Denmark in the Wadden Sea, part of the North Sea, there’s an island known as Mandø. Twice a day the ancient road to the island disappears with the tides, leaving the island out to sea. It’s a historic small island located in the middle of the Wadden Sea National Park of Denmark surrounded by tidel wetlands that can be reached by an unpaved causeway, called Låningsvejen, which is covered by the North Sea twice in every 24 hour period. Mandø is probably one of Denmark's most peaceful islands. That Mandø has been allowed to remain almost untouched by tourism is due to the tides, because at high tide, the island is outside the traffic connection to the outside world.