Bridge tunnels, also known as immersed tube tunnels or submerged floating tunnels, are unique engineering marvels that combine elements of both bridges and tunnels. They are typically used to cross bodies of water where traditional bridges or tunnels are impractical due to factors like depth, navigational requirements, or environmental concerns. Here are examples of notable bridge tunnels from around the world:

Chesapeake Bay Bridge-Tunnel (USA)

Spanning the Chesapeake Bay in Virginia, it consists of a series of low-level trestles, two-mile-long tunnels, and two bridges.

Tokyo Bay Aqua-Line (Japan)

Connecting Kawasaki and Kisarazu across Tokyo Bay, this bridge-tunnel includes a 9.6-kilometer underwater tunnel, making it one of the longest underwater tunnels in the world.

Øresund Bridge (Denmark-Sweden)

While primarily a bridge, the Øresund Bridge transitions into the Drogden Tunnel, an immersed tube tunnel, before reaching the artificial island of Peberholm.

Hong Kong–Zhuhai–Macau Bridge (China)

Connecting Hong Kong, Zhuhai, and Macau, this mega-structure includes a 6.7-kilometer underwater tunnel section.

Fehmarn Belt Fixed Link (Denmark-Germany)

Once completed, it will connect the Danish island of Lolland with the German island of Fehmarn, including an 18-kilometer immersed tunnel.