Underwater Quarry
A partially submerged Quarry in Klysma Nome, that you'll pass through during the Ballad of Si-Mut and Gertha sidequest. Watch out for snakes- they're liberally sprinkled throughout the area.
One treasure is in a little grassy patch overlooking the harbor area, and is guarded by snakes.
The other is underwater in that same harborish area, amongst some smashed urns. Claiming both treasures completes the location.