"Tribes had a treasure chest in the ocean that was missing five treasure items. Each tribe member one at a time had to dive down and retrieve an item then put it in their treasure chest. Once all five items are inside the chest, the tribe swims out to it and carries it ashore. First tribe to bring their chest back to shore would win." ~ @SurvivorWiki
 |  |  |  |
 |  |  |  |
They win the first of three pieces of a map to a hidden treasure chest.
They also send one of their own to loot one item from the opposing tribe's camp!
Proceed to the immunity challenge.