Taiwan Strait Tunnel Project
The Taiwan Strait Tunnel Project is a proposed undersea tunnel to connect Pingtan in Mainland China to Hsinchu in Taiwan as part of the G3 Beijing–Taipei Expressway. It has seen a few academic studies from the China side, but no interest from the Taiwan side, which views such proposals as propaganda.
Source: Wikipedia — Taiwan Strait Tunnel Project (CC BY-SA 4.0)