Construction of buildings in deep sea by conventional methods is extremely difficult. A new technology by using steel fences and anchors, and fixed by inserted rocks, will be demonstrated with the example of efficient vertical Tsunami barriers extending at least 50 m up to 4 km below sea level. New gained land surface and also the fishing farms between Tsunami barrier and shore may compensate most of the costs. Walls and buildings in deep sea may assist deep-sea mining. Vertical walls extending above sea level, preferably protected with hanging triangular structures as surge stoppers, with massive stabilization landward, will replace conventional dikes and levees and will save land areas. Vertical walls of fences extending above sea level, which are circular and filled with rocks, surround pillars to protect off-shore platforms, windpower plants, bridge pillars and other submarine structures.
