In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.

Sentence1: Lilly and Al's dad warned them to look out for sharks in the water. Sentence2: They laughed at him, saying there weren't any sharks. Sentence3: When they weren't paying attention, he swam underwater towards them. Sentence4: He had a fake shark fin attached to his back. Sentence5: They were so scared they ran screaming out of the water.
Lilly, Shark, Lilly and al's dad, Al