From the Tyne Vortex, head down and to the left. Go past the Tyne Wellspring and through the gate.
Head into the Watcher's Hollow one more time. Follow the path around and down.
Keep heading left. There's a silver treasure you can finally get with your new searchlights.
When you enter the room with the cuttlepup, fight off the enemies that spawn, then destroy the glass gate.
Continue down into Seagarden.
Head down and left to find Swish and Cara. Repair the seahorse.
The freshly repaired seahorse will open a tunnel for you.
Head through the gate and into a nihilistic conversation with the Elder Seadragon.
Once you are returned to the chamber with Cara, the seahorse and Swish, head straight down past the Tyne Wellspring. Use your searchlights to go past the anemones.
Use Merryn to keep heading down and collect a green treasure by scaring the snakes and another in the chest for a total of 600 coins.
Head back to the sub, then up and to the right. Go past the crab and stick to the ceiling as you move right. Ping your sonar in the alcove you find to reveal a hidden passage containing a gem worth 200 coins.
Back out of the alcove and head down. Let the current carry you further right.
Head straight down from where it deposits you. Follow your path around the broken turbine and the Merrow eggs, then keep heading down and right.
At the bottom of this path is a chest. Point the sub's searchlight at the anemone, then use Merryn to retrieve the red gem.
Continue to the right, through the glass gate and into the Merrow Ruins.
Keep heading right. Use your sonar to activate the sonic lock and enter the tunnel into the Forbidden City.
Head straight up through the anemones to find a Tyne Collector. There's also a red gem in a chest to your left.
Head to the right on your way down to collect a silver treasure among the anemones.
Sneak past the Cyclops again by hiding out of range near the ceiling, then moving past.
Pass the next Cyclops and keep heading down. Turn right at the bottom.
Straight across from where you exit, your new seahorse friend will let you into a room where you will face several waves of enemies while he watches and does nothing.
After you defeat the enemies, head to the bottom right corner of the room and trigger the red lever you find there to open the next gate.
Use the provided ledges to sneak past the Cyclopses (Cyclopsi?) you find there.
Head to the upper right first to find a red lever to hit. This opens a gate below you.
Head to the bottom right to find the lever to open the door.
There's an ominous Tyne Wellspring waiting for you on the other side. Keep going past to face your most difficult guardian yet. The fight is the same, but this time it's interspersed with a few waves of other enemies as well.
Take the path up at the branch to find a green treasure worth 300 coins.
Head back down and take the other path right and down. There's a chest waiting for you at the bottom containing a red gem.
Head right and then down. Use a sonar blast to break the glass and expose the lever to open the gate below you.
Use the handle at the bottom of the next room to open the gate down.
Keep heading down to find a Tyne Wellspring and hermit crab. Feel free to upgrade any part of your sub you'd like at this point. We focused on the Tyne and Repair upgrades to better prepare for the upcoming fight against the Rimorosa.
Head up and to the right. As soon as you exit, start heading down and into The Caverns of Madness.
Break through the glass wall you see on your right to find another Tyne Wellspring.