Submerged structures / Lake dwellings

Submerged settlement in the Zürich Lake investigated in 1854 by Forel, Morlot, and Troyon.

The sea level in the world's oceans has remained nearly unchanged during the last 1000 years or more. One exception is the middle and north Baltic Sea, where the sea-bottom is rising. Remains of ancient dwellings or cities can be found underwater for various reasons:
A:  The sea level may have risen locally, like the Swedish Vättern lake, as well as the La Tène and Charavines lake settlements in Switzerland.
B:  The dwellings may have been built on water. Examples are the Bulverket fortification and the crannogs of Ireland and Scotland.
C:  The land has sunk after seismic activity (not in northern Europe).
  

Various lakeside & pile dwellings

• Submerged settlement in the Bay of Wismar, Harald Lübke, Germany. Remains of dwelling from c 2000 BC, now submerged.
• Archäologische Kulturdenkmale und Denkmalschutz am Bodensee, Helmut Schlichtherle. Maritime cultural heritage in Lake Constance.
• Bulverket fortification, Gotland, Sweden. Mysterious Medieval c 170x170 m square shaped fortification in a lake, apparently never used and abandoned shortly after construction in the 1130s AD. Several houses and three boats have been found.
• Leben auf dem Wasser, pile dwellings, Archäologie Online
• Alvastra pile-dwelling, National History Museum, Sweden. Dated to c 3100 BC.
• Pile-dwellings, unterwasserarchaeologie.de
• Lake dwelling, Columbia Encyclopedia
• Submerged settlement in the Zürich Lake, Switzerland. Pile dwellings investigated in the 1850s.
• Pfahlbaumuseum Unteruhldingen, pile dwellings in Bodensee Lake, Germany
• La Tène, prehistoric Celtic pile dwelling, located in 1857, Switzerland
• Colletière, Medieval lake settlement, France. Partly submerged after water level rise.

Crannogs

• Crannogs, Cavan, Northern Ireland
• Scottish Crannog Centre
• Lake Settlement Project, Ireland, Aidan O'Sullivan

Various submerged structures

• Cosquer Cave, near Marseilles, France. Discovered in 1991 or '92, partially submerged cave with stone-age paintings, at least 27000 years old.
• Black Sea mesolitic settlement. Stone-age settlement found in 2000 by the Robert Ballard team, on 95 m depth off the Turkish coast. The site seems to be from before the flood, at least 7000 years old. More info.
• Submerged forest & possible ancient ship, the Solent, south England, forest dated to c 4300 BC
• "Seahenge". Cult site in Norfolk, England dendro dated to 2049 BC. English Heritage has decided to conserve the site. Perhaps it will eventually be open to the public.
• Dvaraka/Dwarka. Remains of Indian settlements from 1500-1400 BC and later, submerged or washed away in the Arabian Sea. Investigated since 1979. Ref British Museum Encyclopaedia of Underwater and Maritime Archaeology.
• Oldest Bridge across the River Thames, Eton Rowing Lake, England, 1400-1300 BC
• Bridge across Shannon, Ireland. In 804 AD a 120 m long wooden bridge was built across the Shannon River. Investigated by divers '97-98.
• Tallinn Bay Marine Fortifications, Vello Mäss. Possibly 18th century AD.

Probable natural sites

• Underwater "Pyramids" at Okinawa, Japan. Unidentified (probably natural) structures. Link.
• Mysterious Deep Water Sonar Images Off Western Cuba. "Regular shapes and patterns" were recorded on the seabottom in 2000. The site is known as the "MEGA site". Is it natural or not? Since the depth is 650 metres, it is likely to be natural, but it remains to be investigated. Located in 2000 by Exploramar/ADC, the same company that discovered USS Maine. To be examined in 2002. Link. Link. Link. Link. Link. Link. Link. Link.
• Gulf of Cambay, Indian west coast. Strange objects from the seafloor, but they appear natural, and not man-made artefacts.