Mali ac Ogof y Môr-Leidr

One morning, Mali's dog Gelert goes missing and the whole island are sent searching. On her search, Mali and her friend Dylan hear a noise coming from a cave and decide to follow it. As they head deeper into the cave, Mali and Dylan finally find Gelert but the tide begins to rise. Will Mali, Dylan and Gelert be able to make their way out of the cave before the tide comes in?