Misty Island Tunnel

Misty Island Tunnel is a tunnel under the sea connecting the Island of Sodor to Misty Island, which was introduced in Misty Island Rescue. The tunnel entrance on Sodor is right next to the Sodor Search and Rescue Centre.

When Thomas, Bash, Dash and Ferdinand go into the tunnel, they discover that it's very twisty until they find a rockfall blocking their path. Whiff and Percy go into the tunnel from Sodor to find the rockfall as well.

Trivia

 * Misty Island Tunnel consists of a brick and stone structure at both outlets with, oddly, a giant hollow log somewhere in the middle.