Sword of the Sea Boiling Cavern: All Shells & Secrets

What to Collect in Boiling Cavern

Lava hides more than a dangerous route through the seventh chapter. This Sword of the Sea Boiling Cavern guide walks you through five secret shells, three stele messages, and the Frog Skeleton in progression order. Collecting these finishes the chapter’s shell hunt and can complete your remaining lore and frog trophies before Sky Abyss.

Keep these objectives on your checklist:

• Five secret shells: Collect all five for Boiling Cavern Shell Collector.
• Three stele: Read The Fires Below, The Army of Red Fire, and When Water Battles Fire. These are the final entries in the game’s set of 23.
• Frog Skeleton: Find the skeleton perched on a lantern to earn Frog Skeleton.

The chapter’s water points are all required for progression. There is no separate cleansing trophy here, so focus your optional exploration on the shells, stele, and frog.

Official page: Sword of the Sea (swordoftheseagame.com)

Opening Chambers: First Two Shells and The Fires Below

Image: Steam / Giant Squid

Shell 1: Behind the Left Pillar

In the opening lava chamber with floating boats, look for the rocky pillars on either side. This is also where the snake-like enemy first appears in the chapter.

1. Head toward the pillar on the left.
2. Move around its back, keeping your crossing quick to limit lava exposure.
3. Collect the shell on the small ledge behind it.

Look behind the pillar before leaving this chamber. The shell is tucked out of sight from the main route.

Stele 21: The Fires Below

Solve the first water-bubble puzzle and pass through the door it opens. In the next room, head right and look behind the rock to find The Fires Below.

Read it before climbing the rocks nearby; those rocks lead toward the next shell.

Shell 2: Upper Ledge Beyond the Stele

1. Climb the rocks behind the stele on the room’s right side.
2. Follow the elevated path clockwise around the chamber.
3. Cross the gap toward the large archway.
4. Continue to the far upper platform to collect the shell.

Use the stele as your starting landmark so you can distinguish this elevated detour from the route onward.

Large Boat Chamber: Two Shells, a Stele, and the Frog

After the downhill sequence alongside the snake, you reach another broad lava chamber filled with boats. Search both sides of this area before progressing.

Image: Steam / Giant Squid

Stele 22: The Army of Red Fire

Stay along the right side of the large boat chamber. Follow the edge around the corner to find The Army of Red Fire.

The sideways boat used to reach the next shell is nearby.

Shell 3: Cave Above the Sideways Boat

1. Find the boat lying on its side in the lava on the right.
2. Use its hull as a ramp to reach the raised stone ledges.
3. Follow the narrow ledges to the right, toward the shark statue.
4. Enter the small cave or alcove at the end to collect the shell.

Look for the boat’s tilted shape when orienting yourself. It marks the beginning of the climb.

Shell 4: Narrow Corridor on the Left

The next shell is in the same large chamber, toward its left side near the entrance.

1. Locate the round platform that provides a resting spot above the lava.
2. Look past it for a thin opening through the rock.
3. Move quickly through the corridor.
4. Collect the shell at the back.

Line up your approach from the platform before entering the gap. This route requires a quick crossing through the hazardous passage.

Frog Skeleton: Lantern on the Elevated Boat

At the platform holding the water ball in front of the large door, turn right.

Cross the boat, then climb toward the boat resting on the tall platform. The Frog Skeleton sits on top of a lantern there. Approach it to earn the Frog Skeleton trophy or achievement.

Skeleton Rails: Final Stele and Fifth Shell

The next collectible stop is the chamber containing skeleton spines you can grind.

Image: Steam / Giant Squid

Stele 23: When Water Battles Fire

Follow the skeleton rails to the second level. At the end of the second skeleton, find and read When Water Battles Fire.

If you have read every earlier stele, this completes all 23 messages and earns Wisdom of the Ancients.

Shell 5: Ledge Behind the Statue

From the stele, look behind it toward the statue and the raised ledge.

1. Jump onto the ledge behind the statue.
2. Follow the short side route to the hidden shell.
3. Collect it to finish the chapter’s five-shell set.

Picking up all five awards Boiling Cavern Shell Collector. The vendor’s shell is a separate reward, so you do not need that purchase to finish this chapter’s shell trophy.

The Vendor Shell and Water Whisperer

If you have every chapter’s shells but are still short of the full collection, check your vendor rewards.

There are 50 secret shells across the game. The five hidden here are shells 45–49 in the full collection; the remaining shell comes from the vendor’s final trade.

• Final trade cost: 5000 Tetra.
• Total cost across all five vendor rewards: 8550 Tetra.
• All vendor rewards: Earns Loyal Customer.
• All 50 secret shells: Earns Water Whisperer and unlocks water rails in every level.

Collect Tetra from treasure chests, fish tiles, exploration, and trick attack rewards to finish the trades. Vendor progress carries into New Game+ and Chapter Select, where Tetra sources become available again.

Sky Abyss contains no collectibles, so finish any outstanding exploration here before moving into the final chapter.

Tracking Missing Collectibles on Replays

Chapter Select unlocks after completing the story and lets you return for missed collectibles. Use its tracker to check your progress before repeating the entire cavern.

Several updates make collection cleanup easier:

• August 29, 2025: Added a UI animation when collecting secret shells and made platforming to certain secrets less demanding.
• September 19, 2025: Added collectible tracking to Chapter Select and the New Game+ pause screen.
• September 19, 2025: Fixed incorrect collected-item counts that could prevent an associated trophy from triggering.

On replays, stele text can reappear even after you have previously read the message. Use the three names above as your checklist instead of relying on the pillar’s glowing text alone.