This location is in the same section of lake where you look for medicine pots during The Healer quest. Your location objective is to loot the three treasures. Use Senu to scan for underwater ruins, which will show up as staircase icons.
Two of the lootables are in the first ruin, near the pillar and the medicine jars, and one is in the more westerly ruin. You can use your pulse to help you locate items underwater (and there is some miscellaneous loot to be found). You can also mindlink to Senu while underwater, but your oxygen still depletes at the same rate, so this is not advised.
Snag all three treasures to complete this location.
