China is considering constructing the world's largest undersea tunnel. Proposals for the tunnel, which could cost around $36 billion, will be submitted in April.

First the Great Wall of China, and now the great underwater tunnel?

China currently plans to build the world's largest undersea tunnel, which would connect the cities of Dailan and Yantai.

"Work could begin as early as 2015 or 2016," Wang Mengshu, an expert at the Chinese Academy of Engineering, told the China Daily. The connection would eliminate 800 miles from the current route between the two cities.

Currently, the longest underwater tunnel is the Channel Tunnel linking Britain and France. Out of its total length of 31.6 miles, 23.6 miles are under the sea.

The second longest tunnel is the Seikan Tunnel, at 33.5 miles long. Of that, 14.2 miles of the tunnel are underwater, and the tunnel connects Honshu and Hokkaido, Japan.

The proposed tunnel in China would measure 76.4 miles with nearly 75 percent of the transit underwater, and it would be larger than the Channel Tunnel and the Seikan Tunnel combined.

The project would cost an estimated $36 billion with a completion date in 2026.