Misty Island Tunnel

Misty Island Tunnel is a tunnel under the sea connecting Sodor to Misty Island.

History
During the construction of the Sodor Search and Rescue Centre, the Fat Controller decided to build his new office inside the old tunnel, but Whiff insisted that it wasn't a good idea as it connects to Misty Island. When Percy saw Thomas' smoke signals coming from Misty Island, Whiff and Percy used the old tunnel to find Thomas and the Logging Locos. Afterwards, Misty Island Tunnel was restored and officially reopened. It is currently the most common way for the engines to travel between the two islands.

Trivia

 * In real life, such a tunnel could not exist, as the steam would make the air toxic and suffocate the engines' crews.