AbstractWhen is a Submerged Floating Tunnel competitive?The various elements in transport systems are most often selected on the basis of the lowest price for the alternatives being viaducts, bridges or tunnels or some combinations of these.The submerged floating tunnel will therefore have to compete with well known structures and therefore have a disadvantage since no submerged floating tunnel has yet to be built.A future owner is then faced with a risk not easily estimated on one hand, on the other hand this new alternative may have certain attractive features especially when environmental considerations become important.This paper presents these various advantages and also points out some obvious disadvantages with this new and challenging structure.A great step forward would be if a submerged floating tunnel were built somewhere. The proposed structure here in China would certainly generate a lot of interest and I suggest the involved parties should prepare for a large number of visitors.