Hey Travelers! I just spent the most satisfying afternoon solving one of Fontaine's coolest (literally!) puzzles: the Boiling Water Lake on Elynas. This was such a fun and layered challenge added back in the 4.0 update, and it's still one of my favorites for its clever multi-step design. It's not just about braving the heat; it's about uncovering a whole secret underwater world! If you're wandering around the Beryl Region and see steam rising from a lake that hurts to touch, you're in the right spot. Let me walk you through the complete, chill solution to turn that scorching soup into a refreshing dive spot. 🏊‍♀️💎

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First things first, let's find this sizzling spot! 🔍

The Boiling Water Lake is located on the island of Elynas in the Beryl Region, southwest of the Court of Fontaine. It's super easy to get to! You have two great teleport options:

  • The Statue of the Seven on the island. The lake is just south of it.

  • A Teleport Waypoint on a cliff directly south of the lake, giving you a perfect bird's-eye view.

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Once you arrive, you'll see the water bubbling away. Stepping in causes constant damage, so don't go for a swim yet! The mini-map will also show a Hydroculus icon underwater, teasing you with the promise of loot below.

🌊 Part 1: Solving the Lake-Side Puzzle

This first part is all about manipulating three Water Volume Detection Crystals around the lake's perimeter. Each one is trapped and needs to be freed in a different way. I recommend a Pyro character (for vines) and a character aligned with either Pneuma or Ousia energy.

Here’s your crystal liberation checklist: ✅

Crystal Location How to Free It
North of the lake Use a Pneuma or Ousia-aligned attack on the block.
Southwest of the lake Burn away the thorny vines covering it with Pyro.
Southeast of the lake Defeat the group of enemies guarding it.

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After freeing them, they'll float to new positions. Now for the fun sync move!

  1. Glide to the rock in the middle of the boiling lake.

  2. Grab the Miraculous Hydrograna floating near a Common Chest.

  3. While holding the Hydrograna, activate all three crystals at once. This requires a bit of positioning to be in range of all three—patience!

Success! The chest unlocks, giving you 10 Primogems. More importantly, a Hydro portal appears above it. Dive in! This is your ticket to the next phase.

🕳️ Part 2: The Secret Underwater Lava Cave

The portal whisks you into a stunning, initially dry, lava cave. Your new mission: extinguish the three eternal campfires surrounding the central volcano. The atmosphere here is amazing, but those fires keep it way too toasty!

Step-by-Step Fire Extinguishing Guide:

  1. Clear the area. Start by defeating all the Pyro enemies lurking around. A good Hydro applicator is your best friend here.

  2. Find the three Hydro Cores. These glowing blue orbs are the keys. Each is hidden near a campfire:

    • One is inside a Hydro Amber that needs to be shattered.

    • One is concealed within a barrel of Hydro Slimes.

    • One is tucked inside a wooden crate near the cave entrance.

  3. Insert each core into its corresponding pedestal. These pedestals are right next to each campfire. Placing the core will douse the flames with a satisfying splash!

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With all three fires out, a Hydro Totem appears. Hit it with any Hydro attack, and... get ready for the magic! 💦

The cave floods instantly, transforming into a beautiful underwater cavern. It's one of those gorgeous Genshin moments.

⚔️ Bonus Boss & The Grand Finale

As the water settles, two things happen:

  1. A chest appears—don't forget to loot it!

  2. The Local Legend: Iron Viscount spawns. This is a tough mini-boss, but here's a pro tip: you can use the ability of the nearby Xenochromatic Armored Crab to counter its attacks effectively. Fighting him is optional! You can completely skip him and come back later if you want. Beating him doesn't affect the puzzle solution.

To exit, swim toward the Hydro Current behind where the Iron Viscount appeared. It will propel you upward through a tunnel.

Here’s what you'll find on the other side:

  • The Hydroculus that was teasing you on the map! Finally, it's yours.

  • Keep swimming up to surface in a small, ruined room.

  • Exit either by using the Hydro portal or climbing the stairs.

🎉 Mission Accomplished!

You emerge right back at the lake... but it's completely transformed! The water is calm, cool, and perfectly safe. You'll instantly unlock the "Core Cooling" Achievement and can finally dive in to claim your rewards:

✨ Your Well-Earned Loot:

  • The Hydroculus you detected earlier.

  • A glorious Luxurious Chest sitting on the now-accessible lakebed!

This whole puzzle chain is such a rewarding example of Fontaine's design—it feels like a mini-adventure with exploration, combat, puzzle-solving, and a stunning environmental payoff. It's more than just a chest; it's about changing the world itself. So if you see steam rising in Elynas, you now know exactly what to do. Happy exploring, and enjoy your cool new swimming spot! 😎👏