 Submerged floating tunnel

A submerged floating tunnel (SFT), also known as submerged floating tube bridge (SFTB), suspended tunnel, or Archimedes bridge, is a proposed design for a tunnel that floats in water, supported by its buoyancy (specifically, by employing the hydrostatic thrust, or Archimedes' principle).The tube would be placed underwater, deep enough to avoid water traffic and weather, but not so deep that high water pressure needs to be dealt with—usually 20–50 m (60–150 ft) is sufficient.