Follow Swish up and right through the gap in the rocks.
Keep heading up until the current grabs you and pushes you to the right.
Head up and to the left to find a cuttlepup and a glow bulb you can carry.
Get the cuttlepup to follow you down, then throw the glow bulb through the stinging anemones to get the cuttlepup to clear them out of your way.
Head left to pick up a treasure worth 10 coins and grab the glow bulb before your cuttlepup gets bored and leaves.
Head straight down and around the turbine to find the merrow eggs and another 10 coin treasure. Grab another glow bulb any time your cuttlepup gets distracted.
Use the glow bulb to clear the lantern jellies out of your way as you move left, keeping your cuttlepup in tow.
If you head down and to the right, there's a long passage of anemones that will lead to a 200 coin gem. If you really want the coins, it's worth the trip, but it's difficult to keep the cuttlepup's attention the entire time.
Your goal is the head to the left-most tunnel up with the cuttlepup behind you. Throw the glow bulb up to get the cuttlepup to chase it, then rush up to grab it.
Repeat this process until you get to the turbine. Exit the turbine up and head left to find your freshly repaired sub. Really, it's the least the crab could do considering how many coins you've kicked his way.
If you have the coins, pick up the High Speed Sonar and the Energy Dampening from the crab while you're here. The Sonar Blast is useful, but it's slow to recharge and drains your Tyne energy very quickly.
Head down and to the left to find a dying Cara.
Head up and to the left to find several more treasures. Above the turbine and past the bomb dispenser, there's an invisible chest with a treasure worth 500 coins.
Grab the bomb and spin around the turbine. Use the bomb to destroy the metal wall.
Head down and to the left. Grab a glow bulb and make your way right. Toss the glow bulb up to get the attention of the cuttlepup above you.
Get the cuttlepup to follow you right and through the anemones. Follow the tunnel up and to the right. Keep tossing the glow bulb up through the anemones. The tunnel will lead you up to the Full-Spectrum Search Light, an upgrade for your searchlight that will let you drive the anemones away without the help of a cuttlepup.
Head back down and to the left until you see a glass gate. Use your sonar blast to destroy it.
Follow along the ceiling until you see an anemone-lined hall. Head up it to grab a gem worth 200 coins. On the left, you'll find some sea snakes that will give you another 200 gem coin.
Head back down and to the left until you see a Tyne Wellspring.
If you have the coins, visit the crab and pick up the Missile Defense upgrade for your sonar for 1,000 which will let you defend yourself against enemy torpedoes.
Head left and straight down.
Down in the darkest parts of The Maw, you'll have your first encounter with Red Reapers. Don't try to fight them because you won't win. Just keep moving away from them and leave your searchlights off, even in the dark. Keep using your sonar to navigate. The reapers stay on fixed patrols and only notice you when you are close. Keep pinging your sonar and go slow to avoid their one-hit-kill attacks.
Stick to the right wall on your way down until you see a tractor beam. Head through the tunnel behind it for a Tyne Collector.
As you enter the Bone Vaults from above, head to the right to find an invisible chest on the skeleton.
Keep heading down until you see a Tyne Wellspring and hermit crab.