Thirteen-year-old Dylan and his friend Ali are holidaying on a Great Barrier Reef tropical island.
They are excited about seeing all the coral and fish they have heard about, but trouble with their snorkelling gear and sunburn ruins their first swim.
After messing up their booking, the boys eventually go on a coal and fish sightseeing tour. They see beautiful coral and spot a manta ray and are impressed, but Ali is scared by other big fish nearby.
Looking for more excitement, the boys decide to swim on the other side of the island, but deep water and ocean currents are more dangerous than they anticipated.