This is level 9 of the Way Back.
(Note: Since you can only use the Duplicator in parts 8-16 of this tunnel, he will be the only recommended character.)
If you just beat Level X and clicked part 8 of this tunnel, after the Duplicator fell out of the boat, you were immediately skipped to here. If you haven't used the Duplicator before, you will have to learn how to control him.
Find one of the long rows of ice tiles near the corners of the tunnel and jump across them. Even if it looks like you are going to fall out of the tunnel, sometimes a duplicate may survive because the Duplicator can swap places with his duplicates.
New Level Edit
Although beating this level launches you into playing part 10, you can now use the back/next buttons to play part 8. Note that even though part 8 features on the Galaxy Map, you still cannot access it there. Clicking it will play the cutscene "Boat Ride" and skip you to part 9.