The Horizon Forbidden West Deep Trouble quest is one of the game’s first side quests, and it’s also one of the more vague ones.

You’ll get your first taste of underwater exploration and a good lesson in finding puzzle solutions without the Focus’s guidance.

Deep Trouble: Find the Missing Miners

Head into the mines, dive down under the rocks, and swim into the open chamber. Turn right, and you’ll see a small, light blue patch and an even smaller gap in the rocks. That’s your sign – both here and in future underwater areas – that an underwater passage is there for you to take. This one is much longer, but you can press “Triangle” to boost and swim faster (at the expense of some oxygen).

Once you surface again, the miners are just ahead. Speak to them for the next step.

Deep Trouble: Drain the Mine and Go to the Mine Cart

This part takes you on a detour around the mines so you can ignite an explosion and drain the water from the mines. Facing the miners, turn left, walk off the platform, and dive down. There’s another short tunnel here, and you’ll emerge in the cavern with the minecart.

Ignore the ladder to the right, since you can’t get to it yet. Hop in the water, and swim across to the small ladder in front of you, then jump up to the other ladder, and turn left. Follow the passage into the next room, then drop into the water.

You can be stealthy here to avoid the Burrowers using the stealth plants, though it’s possible to just defeat the nearest one and clamber over the rocks to reach the mine track. Either way, follow the cart track around and back into the other room.

Use the Pullcaster to swing the beam over, leap onto it, and interact with the cart.

Draining the mine attracts more machines. Deal with them, then speak with the minors to complete the quest.

Check out our other Horizon Forbidden West guides for more tips, including machine weaknesses and the best skills for Aloy.