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Once Human Diving Guide: How to Dive Underwater, Diving Suits & Oxygen

LiveUpdated 2026-10-23 · Game v3.1.1Deeper water = more pollution

By the Once Human Guide crew — a small fan team led by Yao · from patch notes + videos

Short answer: Put on a Diving Suit before you swim in the sea: without one you lose health in the water. Underwater you manage three things: pollution (Diving Suit, Fish Oil Paste, Anglerfish), oxygen (Oxygen Tank, Bubble Fish) and cold (Fish Oil Paste, food). The deeper you go, the higher the pollution and the more dangerous the creatures.

Hazards on the way:Black Tide · Clots cost SanityMist of Deceit · coldin Misty Marsh · Reefshadow Bay
On this page
  1. Before you start
  2. How to dive, step by step
  3. Diving gear and items
  4. Food for diving
  5. What to look for underwater
  6. Fix: losing health underwater
  7. FAQ
  8. What changed

Before you start

Diving gear comes from the scenario’s ocean Tech subjects, which cover diving, protection, fishing and manufacturing. The diving gear itself needs Black Tide Clots, a Haywire resource you gather in the black water of Misty Marsh; gathering them costs Sanity. How each Haywire sea works: Haywire zones.

Exact recipes, the button to dive and the oxygen timer are not confirmed yet.

src: dev blog (2026-10-16) · Doomeris zIDlwmX7CPg @12:20

How to dive, step by step

  1. Swimming in the sea without one drains your health. The suit gives basic protection from sea pollution and makes you swim faster.

    src: Open World Games 1_YBnzhRRZ8 @11:00 · patch notes

  2. An Oxygen Tank, an Inflatable Float for a quick climb back up, and Fish Oil Paste for cold and a short break from water pollution. Add food for the dive (table below).

  3. Glowing algae on the surface hint that something is below. Treasure maps point you to underwater ruins. One trick from a creator: in Build Mode, switch to free cam and move the camera under the water to look before you dive.

    src: dev blog · patch notes · MaleOreo d6qDYAK-qkQ @10:00

  4. The deeper you go, the higher the pollution and the tougher the creatures. Swim near an Anglerfish to stay clear of sea pollution, and catch Bubble Fish bubbles to refill oxygen.

  5. Guns don’t work underwater. Sharks track you and attack in bursts; decide early whether to fight or swim off. One creator found a submerged shark couldn’t be killed with ordinary weapons. one creator’s video

    src: Doomeris zIDlwmX7CPg @06:20 · MaleOreo d6qDYAK-qkQ @08:41

  6. Use an Inflatable Float to rise fast. Throw an Air Cushion for a short-lived platform on the surface. On the ship, take the suit off: it slows you down on land.

    src: patch notes · SysFem64 WNM-tSNh52w @00:40

Diving gear and items

Tick what you already carry. Quantities and recipes are not confirmed yet.

have item what it does
Basic Diving Suit basic protection from sea pollution
Shark Diving Suit stronger pollution protection, faster swimming
Oxygen Tank turns on by itself when your oxygen runs out
Fish Oil Paste raises temperature resistance, briefly blocks water pollution
Inflatable Float one-use, fast ascent
Air Cushion thrown; a floating platform that lasts a short time
Spear Gun underwater weapon
Black Tide Clots material for diving gear, Misty Marsh

src: patch notes (diving equipment) · dev blog (Haywire resources)

Food for diving

dish or drink effect
Stealth Cuttlefish Sashimi underwater enemies notice you from a shorter range
Silky Fish Oil Soup lowers what swimming costs you
Fresh Fish Dishes restore Energy, lower hunger and thirst while swimming
Heavenly Calm Soup more seafood in it = more Sanity recovery and pollution resistance

src: patch notes (food and drinks)

What to look for underwater

  • Shipwrecks in shallow water are the place to start; sunken buildings, coral mineral clusters and underwater laboratories sit deeper.
  • Treasure maps come from beachcombing, fishing, quests and settlements; drift bottles can hold them too. Follow them to underwater ruins.
  • Underwater Haywire chests: on the final test build they held weapon and armor parts for tier 3 gear. final test build, may have changed
  • One creator’s routine: wear the Diving Suit plus a Black Tide Protective Mask, sail to the map’s spot, then dive for the wreck or lab. final test build

src: patch notes (Underwater Exploration and Treasure Hunt, Beachcombing) · Gotcha Beast KJvFq__cWp8 @11:50, @12:00

Where each sea sits: Isles of Abyss map. For hunting sea creatures from the ship instead: Ship cannons.

Fix: losing health underwater

  1. No Diving Suit. Swimming in the sea without one costs health.
  2. Out of oxygen. Carry an Oxygen Tank, look for Bubble Fish, or use an Inflatable Float to surface.
  3. Too deep for your gear. Pollution rises with depth. Upgrade to the Shark Diving Suit, eat Fish Oil Paste, or stay near an Anglerfish.
  4. Cold. Fish Oil Paste and warm food raise temperature resistance.
  5. Shark on you. Guns don’t work underwater. Use the Spear Gun or head back to the ship.

FAQ

How long can I stay underwater?
The oxygen time is not confirmed yet. An Oxygen Tank kicks in automatically when your oxygen runs out, and Bubble Fish bubbles refill it, so carry a tank and look for Bubble Fish on long dives.
Can I use guns underwater?
No. Firearms don’t work in the water; use the Spear Gun or harpoons. From the ship, a Harpoon Cannon can hit creatures below the surface.
Why do I lose health while swimming?
You’re swimming in the sea without a Diving Suit. Put one on before you go in.
Should I keep the Diving Suit on?
Only in the water. The suit makes you swim faster but walk slower on land, so take it off once you’re back on the ship.
What is the Shark Diving Suit?
The upgrade to the Basic Diving Suit: better protection from sea pollution and faster swimming. Its recipe and unlock step are not confirmed yet.

What changed

  • v3.1.1 · 2026-10-23Page created.

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