3 Loot Treasure
Dive down where you see the debris (where the icon is on the map), head inward.
Soon you can dive up again. Here's Treasure 1 next to a dead body.
Another dive is ahead. Jump down on the other side. Dive through the underwater corridor and dive up into hostile area.
In this pool here is Treasure 2
Here, in the camp area, is Treasure 3