This page explains how to complete the Shadowbringers Main Scenario Quest "Waiting in the Depths".
This quest is available if you have completed the quest To Storm-tossed Seas.
Starting the Quest
Talk to Thancred in the Tempest to begin the quest. This area can be reached from Kholusia by speaking to Inewyl at Venmont Yards (south of Wright).
Search for Anything Unusual
Go southeast to where the orange arrow is pointing in the minimap. Go to the southeast part of the orange circle and check on the Ondo Youth to proceed.
Speak with the Ondo Youth
Go southeast to where the orange arrow is pointing in the minimap. Attune to the Aetheryte, then go to the quest icon on the map and talk to the Ondo Youth to proceed. There will be a cutscene.
Speak with Alphinaud
Go to the quest icon on the map and talk to Alphinaud to proceed.
Defeat Blue Swimmers
Go northwest through the archway and go north from Pulshs Ooan (who is standing just beyond the archway). Go north until you can go northeast to where the orange arrow is pointing in the minimap. Enter the cave and go through the tunnel until you see quest icons in the minimap. Go to a quest icon to find a Blue Swimmer. Defeat it, and repeat the process until you have defeated three of them.
Speak with Paushs Ooan
You can either teleport to the Ondo Cups, or you can go southwest to exit the cave, and continue going southwest until you can go southeast to the quest icon. Talk to Paushs Ooan to complete the quest. There will be a cutscene.
Aether Current Quest
With the completion of this quest, you can now start the blue quest "Koal of the Cups" in the Tempest. Completing that quest will attune you to an Aether Current in this area.
Next Main Scenario Quest
After you complete the quest, talk to Y'shtola to accept the next quest: City of the Ancients.