This achievement can be gained in Film 2 - Chapter 5 - The Kraken.
You need to get to the actual fight with the Kraken at the end, when you're on the top deck and you can see his heart points on screen. You'll be staring down the Kraken's mouth, hard to miss.
For this achievement, simply jumping into the toothy mouth isn't enough - you have to wait until the Kraken uses its "suck in" attack where it pulls all the little items off the deck. When this happens, jump towards it and you'll be eaten. Repeat 9 more times for the achievement.