submerged floating tunnel

a tunnel that floats underwater, deep enough to avoid water traffic and weather. 
Archimedes bridge, floating underwater tunnel, SFT, SFTB, submerged floating tube bridge, suspended tunnel, underwater floating tunnel

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Wikimedia, Wikidata
tunnel, bridge, 

• Freebase entry^@
  

Frameless

Archimedes bridge

Type	Date	Description	Keywords	Notes	Source
link		Freebase entry@			Wikidata
image	2007	Archimedes bridge			Wikimedia

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