Underwater City

How to get it

The entrance is in open sea, between Frozen Village and the Prison: look for the Whirlpool surrounded by three large rocks and jump into it. The area is small and easy to miss.

Two other approaches exist, less reliable. Coming from Fountain City, you hit an invisible wall: Flash Step goes through it, but it is not recommended. With a flight ability, you can also eventually find the island way off on the map, without going through the whirlpool.

What it looks like

The dome covering the island acts as an atmosphere and keeps the water out. In the center stands a large castle, the lair of the Fishman Lord. The outer edge is lined with tall rocks, and the sandy ground is dotted with large mushroom-like trees.

The island is one of those reworked with Update 30 (Sea 1 Rework): the source changed its illustration image without rewriting this description.

Inhabitants

NPCs	Enemies	Boss
King Neptune, Water Kung Fu Teacher	Fishman Warrior, Fishman Commando	Fishman Lord

King Neptune's quests

The island's secrets (Update 30)

Update 30 hid three secrets in Underwater City. Here is the essential, under their official names:

• Ride the Bubble: spot a coral releasing clear white bubbles and jump into one. It carries you up to the Hidden Cove (the source called it Coral Cave until 28 September 2026), with a dark chest at its center. Interact with the chest: three enemies spawn. Defeat them, then go back down through the whirlpool.

• Scattered Light: to the right of the Fishman Lord's castle, find the crystals with a light going through them and a dark symbol on the wall (a dark patch of sand, said the source until 28 September 2026). Move the crystals not yet hit by the light to reflect the beam onto that symbol: a correctly placed crystal becomes immovable. This frees the Water Kung Fu Teacher, whom you then talk to.

• Awakened Fishman Lord: when the boss awakens, the chat announces "The water is stirring - the Fishman Lord has risen...". Search the nearby clams until you find the one holding the black pearl and claim it: the boss sequence starts. End message: "(your username) defeated the awakened Fishman Lord!". Defeating an awakened boss also grants a roll at the Awakened Boss Gacha.

What it brings: 5 secret levels per secret, 15 for the island, and once all three are done, Underwater City becomes a destination of the Middle Town teleporter (inside the town's central building). If the NPC only gives you 2 levels instead of 5, keep talking to him without leaving the game: it is a known bug.

The full step-by-step walkthrough is on the Island Secrets page.

Good to know

• The Water Kung Fu Teacher hides behind the Fishman Commandos area, right against the back wall: spot the wall section in a different color and go to its left. He teaches Water Kung Fu for 750,000 Beli. Since Update 30, the Scattered Light secret "frees" him; the source does not say whether he remains accessible without doing that secret.
• The Fishman Lord has a small chance to drop the Trident.
• No Blox Fruit spawns in Underwater City.
• All enemies on the island drop Fish Tails, with a low chance.
• One of the Fishman Commandos spawns inside the yellow coral next to the wall.
• The island holds three gold chests and one diamond chest.

Trivia

• Underwater City is one of nine islands to have a Portal, along with Castle on the Sea, Hydra Island, Kingdom of Rose, Cursed Ship, Skylands/Upper Skylands, Tiki Outpost, Submerged Island and Floating Turtle. Here, the portal uses a completely different system and model from the others.
• Together with Submerged Island, it is one of only two islands supposedly located underwater.
• Despite the underwater setting, the dome can be seen from afar as a round island sitting on the water. By finding a gap in the invisible wall near the Fishman Commandos, you can swim to the shell of the dome and walk through it: it has no collision.

• The island is so far away on the map that your avatar may start glitching when you look at it up close.

Update history

Island : Underwater City·Released : Update 3

1. Update 30 28 septembre 2026 Adjustment ▾

   • Ride the Bubble: the cove is called Hidden Cove (Coral Cave before) and the chest is dark; the bubbles come from a coral. Scattered Light: the light is reflected onto a dark symbol on the wall, no longer a patch of sand (source's Island Secrets page, 28 September 2026). Two captures added: the corals and the crystals.

   See update 30

2. Update 30 5 septembre 2026 Adjustment ▾

   • Island reworked with the First Sea rework (Sea 1 Rework).
   • Three island secrets added: Ride the Bubble, Scattered Light and Awakened Fishman Lord (5 secret levels each).
   • The Fishman Lord now has a secret awakened version.

   See update 30

3. Update 3 vers 2019 Release ▾

   • Added to the game.

   See update 3