The advantages and disadvantages of three major underwater tunnel construction methods, including drill and blast method, TBM/shield method and immersed tube method, are presented. Comparison and contrast is made among the three mentioned construction methods in terms of geological conditions, water flow velocity, water surface transportation, cover depth, number of traffic lanes, water leakage, work quantity, construction period, construction safety and construction cost. Finally, major challenges in the construction of underwater tunnels and their countermeasures are analyzed. In the construction of immersed tunnels, the erosion of the riverbed, the phenomenon of the local parts of tube elements being higher than the riverbed and the increasing cover depth are big challenges; in the TBM/shield method, boring under shallow cover, wearing of cutter heads and cutting tools, increasing cover depth, damage of main bearing and boring in fault and fracture zones are big challenges.