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Once Human Ship Cannons: Every Turret & Best Ship Weapons

LiveUpdated 2026-10-23 · Game v3.1.1First cannons in Fragrant Cape

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

Short answer: Each ship cannon has one job: the Harpoon Cannon for sea creatures, the Long Cannon for decks and buildings, the Rapid-fire Cannon for Calamity Tower weak spots and the Shotgun Turret for enemy ships. A common setup is one of each of the first three plus a Shotgun Turret. Bind your main gun to the helm with G so you can steer and fire at once.

Hazards on the way:Giant Squid · grabs hullSkyfire · hits hullsin Fragrant Cape · Falling Ember
On this page
  1. Before you start
  2. Every ship cannon and turret
  3. Mount and fire a cannon, step by step
  4. Best ship weapons for each fight
  5. Fix: cannon won’t fire or can’t hit
  6. FAQ
  7. What changed

Before you start

Cannons are ship facilities: you place them in Build Mode like any other part of the ship, and you unlock better ones through Tech, the same way you unlock hulls and propulsion. Plan cannon spots before you fill the deck. If you haven’t built a hull yet, start with How to build a ship.

The dev blog’s rule of thumb: you can’t use one gun for everything. Each cannon is aimed at one kind of target, and guns with shell drop show a pre-aim line.

Every ship cannon and turret

cannon best against versions when
Harpoon Cannon sea creatures; its shot goes through the water surface basic / elite Phase I
Long Cannon decks and buildings (extra damage) basic / elite Phase I
Rapid-fire Cannon Calamity Tower weak spots basic / elite Phase I
Repeating Long Cannon steady fire on one target not confirmed yet Phase I
Shotgun Turret enemy ships and patrol boats basic / elite Phase I
Frost Cannon slows the target not confirmed yet Phase I
Corrosion Cannon makes the target take more damage not confirmed yet Phase I
Ram close-range hits with the ship itself not confirmed yet Phase I
Naval Mine Launcher drops mines not confirmed yet Phase I
Rocket Launcher not described yet not confirmed yet Phase II
Oil Drum Launcher not described yet not confirmed yet Phase II
Repeating Shotgun Turret Voyagers (very high damage) not confirmed yet Phase II
Freezing Cannon freezes the target not confirmed yet Phase II

src: Isles of Abyss dev blog (2026-10-16), Ship Cannons · damage, range and fire-rate numbers not published

Phase II adds four guns, so don’t sink all your materials into your first-week loadout. When Phase II starts on your server: Isles of Abyss hub.

Mount and fire a cannon, step by step

  1. Early cannons come from Tech. Some higher cannons and support facilities at the bottom of the Archipelago section need reverse engineering instead of Tech points. Cannons, propellers, side thrusters and boosters all need Precision Gear, which one creator got by recycling rare ship equipment in settlements and taking it apart at a dismantling bench. drop not guaranteed

    src: Grizl o5-Cq9fuLF0 @02:01, @04:40

  2. After the ship is finished, try each cannon from its real spot. Check its aiming range and make sure your own walls and facilities don’t block the shots.

    src: Grizl o5-Cq9fuLF0 @06:30

  3. At the helm, press G on a cannon to bind it to the driver’s seat. You can then steer and shoot without leaving the wheel. Other cannons are for crew members when you sail with friends.

    src: MaleOreo d6qDYAK-qkQ @07:41, @08:30

  4. Hold right-click while driving to fire the bound cannon. The selection wheel switches between bound cannons; guns with shell drop show a pre-aim line.

  5. Check your ammunition recipes before you sail and bring what you need for cannonballs and harpoons. A supply bench on board lets you craft more at sea. Mist of Deceit Wicks from Reefshadow Bay are used for cannon shells.

    src: Grizl o5-Cq9fuLF0 @02:40, @06:30 · dev blog (Haywire resources)

Best ship weapons for each fight

No one has published damage numbers yet, so this is by job, from the dev blog and creator setups.

fight mount why
Giant Squid, sharks Harpoon Cannon built for sea creatures and can hit below the surface; one creator found a submerged shark couldn’t be killed without the right tool one creator’s video
Calamity Tower Rapid-fire Cannon, Long Cannon Rapid-fire for weak spots (dev blog); one creator prefers the slower, harder-hitting Long Cannon and repositions between shots
Voyagers (enemy ships) Shotgun Turret + Ram; Repeating Shotgun Turret in Phase II the spread hits more pellets up close, and the Ram works at the same range; leave room to back off one creator’s setup
Sea Calamity Zone (Phase II) Long Cannon (extra damage to buildings, per the dev blog) destroy the outer buildings and their shield cores, set off mines early, and shoot the turret mounts
slowing a target Frost Cannon, then Freezing Cannon (Phase II) slow or freeze it while the rest of the crew shoots

src: dev blog (2026-10-16) · patch notes (Sea Calamity Zone) · Grizl o5-Cq9fuLF0 @05:40, @06:00 · MaleOreo d6qDYAK-qkQ @08:41

A common all-round setup: one creator’s most-used mix is a Harpoon Cannon, a Long Cannon and a Shotgun Turret, swapped depending on the trip. one creator’s setup

For gunners: the new Turret Enhancement mod (Armor Mod, Gloves) raises the damage of facilities you operate. It comes from The Sunken Lord, or by spending Heart of the Ocean in the reward stage of Calamity Tower or The Sunken Lord.

Later tiers: on the final test build, tier 4 ship weapons came from the Tech tree, and end-game cannons dropped from high-level landmarks or the Calamity Owl. final test build, may have changed

src: patch notes (Mods) · Gotcha Beast KJvFq__cWp8 @12:21

Fix: cannon won’t fire or can’t hit

  1. Not bound? From the driver’s seat you can only fire cannons bound to the helm with G.
  2. Out of ammo. Craft more cannonballs or harpoons at a supply bench; bring the materials with you.
  3. Blocked line of fire. Your own structures can block the shot. Move the cannon or remove the part in the way.
  4. Wrong gun for the target. Use a Harpoon Cannon for creatures below the surface; other guns may not reach them.
  5. Shell drop. Long-range shots fall; follow the pre-aim line.

FAQ

How do I switch between cannons while driving?
At the helm, press G on a cannon to bind it to the driver’s seat. While steering, hold right-click to fire it, and use the selection wheel to swap between the cannons you have bound.
What is the best ship cannon?
There isn’t one gun for everything; the dev blog gives each cannon its own target. For general sailing, one creator’s most-used mix is a Harpoon Cannon, a Long Cannon and a Shotgun Turret. Damage numbers for each cannon are not confirmed yet.
Why can’t I unlock the higher-tier cannons with Tech points?
Some higher cannons at the bottom of the Archipelago section of the Tech tree need reverse engineering instead of a normal Tech point unlock. Check the requirement before you save materials for them.
What do cannons need to fire?
Ammunition you craft. The dev blog lists Mist of Deceit Wicks from Reefshadow Bay as a material for cannon shells. Full ammo recipes are not confirmed yet.
Is there a Javelin Cannon?
The English dev blog doesn’t list one. The Traditional Chinese blog mentions an advanced cannon that fires homing shells, and some creators call a cannon “Javelin”. Its official English name is not confirmed yet.

What changed

  • v3.1.1 · 2026-10-23Page created.

Sources

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