This is part two of our The Last Guardian walkthrough. You can find part one (meeting Trico) here.
The Last Guardian Walkthrough – Part 2 – Escaping the cave with water
Upon escaping the initial section, you'll run up the ledge of some rocks. There are some pots across the path, so use Trico's tail power and blow them up so you can cross. Run some more and you'll discover a giant pool of water. Jump down and swim to the left where there's a ledge with a bunch of wooden boards covering a hole. Have Trico blow up the wood with his electric.
Once inside, climb up the chain and jump to the ledge. Push the box of food off the ledge to break it. Throw each barrel of food into the water. This will encourage Trico to jump down and eat the food.
Once Trico eats the food swim along the rocks and you'll see an indent (just before the waterfall). Call Trico over, climb on top of his back and jump to the ledge.
Run a bit and you'll see a wall with some light poking through. Crawl through the hole until you escape. You'll say goodbye to Trico, but he will jump over the ruins and follow you. Your adventure now begins.