From the first Tyne Wellspring in The Forbidden City, head up and to the right. There's a Formori Cyclops waiting for you.
Duck up onto the shelf to the left and ping your sonar to find an invisible chest and a gold treasure for 75 coins.
Stick to the ceiling as far left as you can and you should be able to avoid the Cyclops' gaze as you make your way right.
Stay near the ceiling and you'll see a silver treasure. Pass it, then go up to the ceiling again and ping your sonar to reveal the path.
Stick to the left as you make your way down past the Cyclops and ping your sonar. The tractor beam with grab you, but you can still exit the sub and grab the treasure for 10 coins.
Break free of the tractor beam and head straight down as far as you can go.
As you enter the large room on your right, head down and to the right. Pass by the inticing-looking chest with the green gem for now and continue down. At the bottom of this room is a Tyne Wellspring and Tyne Vortex.
Head back up to that mechanism with the sonic lock. Opening it will release a lot of enemies, but they're all fairly low-level and you get a green gem worth 100 coins at the end.
Head straight up and into the munitions factory.
Head right and down to enter a room that will lock down as soon as you enter and release several waves of enemies. Defeat them and exit to the right.
There's a button on the floor directly in front of you that will need to get held down by something heavy. Head up and into the room above you.
Your goal is to move the Formori warhead from its spawn point, all the right and then all the way back left without it ever touching the beam of light.
Once you get the warhead through, move it into place on the button.
DO NOT ping your sonar near the bomb or it will go off and you'll have to do it all over again.
You will, however, need to use your sonar extensively in the next room. Clouds of black grease block your view of the winding passage and the mines. Make your way forward slowly. Don't hesitate to use your torpedoes to blow up the mines from a safe distance to clear your path.
Work your way around to find the statue head in the middle of the room. Duck past the two mines there ‒ or blow them up ‒ and install the statue's head to exit.
Keep pinging your sonar and using torpedoes to blow up the mines through the next room as well.
Stick to the left as you make your way up and out to sneak past the Formori Cyclops.
Head right and past the repulsor beacon. Carefully push the warhead onto the button. When you go past, the repulsor beacon will trigger the warhead to explode, so you have to get through the gate quickly.
Continue right where you'll get ambushed by some enemies.
Get right next to the gate and use your sonar to trigger the warhead to let you through.
Wait for the next warhead to drop, then push it to the metal gate on the right. Trigger it with your sonar.
Go straight up until you see another Tyne Wellspring.
Head right, then up.
Use the handle on the right to close the horizontal gate then push the warhead from the left up against the metal wall. Use your sonar to detonate it and claim a gold treasure from the chest.
Push another warhead down through the gap and onto the button to open the gate to your right.
Go just past the gate that just opened and ping your sonar to remove the warhead.
On the other side of the gate is a clockwork cannon and another guardian. Keep moving and throwing the bombs back into the guardian's face.
Once you defeat it, you'll be rewarded with the Ice Shot. Head straight down from where you picked up the Ice Shot and practice using it on the lava wall to your left. If you need to recharge your Tyne energy, pluck the (what we'll call) Tyne Flowers.
Head to the left and along the top. Use the Ice Shot to float the warhead from the left to the right. Once you're clear of the beam, let the warhead fall, then Ice Shot it again to float it up to the metal gate above the Tyne Wellspring. Use your sonar to detonate it.
Go retrieve the statue head. Before you turn around, ping your sonar. Exit as Merryn and go grab the treasure worth 50 coins.
Take the statue head back and install it on the statue.
With a little bit of work, you can use another of these warheads to claim a gem worth 200 coins like in the video below.
Continue left and open the next gate by striking the red lever.
Head straight down and then right.
Float the warhead up with your Ice Shot and through the magma gate.
Head down through the gate you just opened and you'll find a Tyne Wellspring at the bottom of the stairs.
Work your way around and back to below where you started. Ping your sonar and use the levers there to open the gate above the warhead.
Float the warhead up with the Ice Shot and destroy the metal gate above it.
Float another warhead up. Just as it passes the midpoint of the central hallway, ping it with your sonar. The goal is to get it to explode near the lever in the electricity-filled hallway above you.
Exit to the left.
Float the warhead from the bottom right to the button in the top left. You may have to hit it with the Ice Shot again to get it to stay. This will open the gate at the top and get you a treasure for 10 coins.
Continue left. The doors will shut behind you and you'll be faced with several waves of enemies and a clockwork cannon. Take out the enemies and keep moving to avoid the cannon's torpedoes. A red lever will appear in the bottom right of this room. Hit it and then watch the bottom left corner. Another lever will appear. This continues clockwise around the room two more times. Hit the lever four times to open the doors.
Pass through the magma gate to find the next puzzle. Removing any part of the statue will allow the warhead to roll to the left, but the light beams ensure that it blows up before it makes it all the way up to the lever.
Disassemble the statue and block each of the light beams with a piece.
Make your way left and up and trigger the bomb with your sonar. You'll notice a hidden passage on your right that Merryn can travel for a silver treasure.
Keep heading up all the way to the top, then head left and all the way to the bottom.
Ice Shot your way through the magma gate.
Then use your regular torpedoes to blast through the remaining wooden gates.
Head down and fight your way through the enemies until a Nautiloceros appears behind the gate on the left.
Trick the Nautiloceros into smashing through the metal wall blocking access to the lever in the wallson the right. Just hover in front of the wall you want it to hit, then boost out of the way when it charges.
Pull the handle, then repeat this process on the bottom.
There is another metal wall with a couple coins behind it as well as a hidden passage at the top.
Exit to the bottom right.
Pass through the turbine you find on the other side of the gate. When you transfer to the electrified one, take care not to touch the blades.
Follow that turbine around until you can hit the red lever in the upper left. Take the turbine around one more time to exit out the top and continue left and up.
Follow the next turbine around to the stone wall on the upper right. Blow it up to gain access to a warhead dispenser.
Float a warhead into the moving blades. It will fall into the electrified turbine below and to the right, allowing you to push past.
Head down and left for the next Tyne Wellspring.
Enter one of the gaps in the electrified turbine below you. Exit up to room above you to find some boxes and a chest with another Tyne Collector.
The lever to the right starts and stops the turbine on the right. Time it so the non-electrified blades line up and give you safe passage through the turbines.
Keep going up to the next Tyne Wellspring. Exit the sub and swim along the tunnel on the left to find a chest and a silver treasure.
You'll find the statue's head on the right-hand side of that room, caught in a electrified current. Wait for a pause in the current and rush in to retrieve the head, then take it back to the sub.
Install the head to open the gate above the warhead.
Float the warhead up. You'll have to hit it with the Ice Shot again, then block the beam with the sub. Let the warhead push the electrified turbine blades for you until you can enter the gap.
Push the turbine around and exit to the right.
Use the handle in the room below to open the gate into the next room down.
Your goal here is to get a warhead to explode the metal wall to your left. Watch as the warheads roll around the room. Ping your sonar right before it rolls across the gap above you. This should set it to blow at the metal wall to your left and give you access to the lever.
There's another lever below and to the right. Again, watch the warhead as it rolls around the room. Trigger it with your sonar just below the level of the central platform.
Head right to find the next Tyne Wellspring and, even here, a hermit crab.
After all of the treasure hunting we've done, we had enough to purchase both the Tyne Extractor and the Lightning Claw for 800 coins and 2,000 coins respectively to max out the claw's upgrades.
There are a few coins down a hidden passage below and to the right of the Tyne Wellspring.
Head up and use the handle to open the gate above you.
Defeat the guardian on the other side and head to the right.
Stick to the ceiling to find another sonic lock chest that will release a lot of enemies, then give you a gem worth 100 coins.
Head straight down to the bottom to discover Merryn's father's boat.
Attempting to open the cabin of the boat will get you sucked into the Formori machine known as The Architect.