Relic 1 (Bone arrowhead)
Right after you enter the cave and jump down, you find a chest on the left. Examine the arrowhead at the point.
Relic 2 (Enamel Brooch)
In the other part of the cave, by the ledge, at which you exit the Tomb, with the exit path on your right. Examine the reverse side of the brooch and the spoiled image.
Relic 3 (Paiza)
While swimming towards the camp, dive into the recess on your right. Examine the relic by flipping it over to the other side.