Secret Developer Island in How to Fish: How to Get There

Updated 2026-09-02 · Steam How to Fish

The How to Fish secret developer island is a real island scene that ships inside the game but is left out of normal boat navigation, and there are exactly two documented ways to stand on it: install the DevIslandUnlocked mod, or edit a save file so the game spawns you there. Neither route is an in-game unlock, and Dazed Games has never mentioned the island in any patch note from 1.0.4 to 1.0.11. Almost everything about what is on the island is thin and player-reported, so this page separates the confirmed methods from guesswork.

The mod route is the better documented of the two. DevIslandUnlocked (Rompedev, version 1.1.0, 6,316 downloads, last updated 22 August 2026) states on its Thunderstore page that the game already contains DevIsland but that it is not part of the normal island navigation flow. That line, from a modder who hooked the game's own island system, is the strongest evidence that the place is loadable content rather than a rumour.

The two documented routes at a glance

Route	What it is	Needs mods	Reversible	Confirmed source
DevIslandUnlocked mod	Registers DevIsland as a sixth navigable island with a cyan radar dot	Yes, BepInEx 5 Mono	Yes, uninstall the mod	Mod README on Thunderstore
Save file edit	Sets the spawn island field so you load in on the island	No	Only if you kept a copy of the save	Player guide on Steam
In-game unlock	No quest, boss or purchase leads there	Not confirmed to exist	n/a	Nothing in patch notes 1.0.4 to 1.0.11

If a video or comment claims a boat path, a lure or an achievement opens the island, treat it as unconfirmed until a patch note says so.

Route 1: the DevIslandUnlocked mod

Use this route if you already have mods running, since it does not touch your save file. Set up BepInEx first following the mods install guide, then install DevIslandUnlocked with a Thunderstore-compatible manager, or place DevIslandUnlocked.dll in BepInEx/plugins/DevIslandUnlocked/ by hand.

What the README says the mod does:

Unlocks the existing hidden DevIsland and registers it as a sixth navigable island.
Adds a native-style radar point in a dedicated bright cyan colour so it is easy to tell apart from the five normal island markers.
Leaves the marker under the game's own control, meaning it only appears while the normal boat radar is active.
Does not replace or modify the five normal islands.

Crucially, the mod does not move the island. The README is explicit that DevIsland contains content baked for its original world coordinates, and that the mod leaves its meshes, lights, colliders, SpawnManager, IslandHolder and baked content alone, adding only the navigation trigger and radar entry needed to reach the scene where it already sits.

Requirements are How to Fish plus BepInEx 5 Mono, with the dependency string BepInEx-BepInExPack-5.4.2305. After one launch a config file appears at BepInEx/config/com.howtofish.devislandunlocked.cfg with an Enabled toggle, a ShowDevIslandDot radar toggle and a VerboseLogging debug option. If you also run HTF Mod Manager, those settings can be edited from the in-game MODS menu instead.

The Thunderstore page describes version 1.1.0 only as a compatibility update for How to Fish 1.0.5; whether it was tested against any later build is not confirmed yet. Five more patches are documented after 1.0.5, up to 1.0.11 on 1 September 2026, while the mod has not been updated since 22 August 2026. If it stops working, that gap is the first thing to check. See mods not working for triage steps.

Route 2: the save file method players report

The Steam guide "Secret Developer Island" describes a manual save edit. Paraphrased: create a fresh save, quit the game, open %appdata% in File Explorer, go to LocalLow, then Dazed Games, then How to Fish, then Saves, open the text file matching that save, change the SpawnedIsland value to 5, save, then launch and load it.

Three things to know before trying it:

Player-tested, not official. Dazed Games has never documented save file fields, and no patch note endorses editing them.
The value 5 sits one past the last normal island. Player guides editing the same field use 4 for the final volcano island, which is island five in play, so the field reads as zero-based. That matches DevIslandUnlocked calling DevIsland a sixth navigable island.
Patch 1.0.11 changed how saves are handled. The 1 September 2026 notes say save files are now always checked that they are not corrupt before loading, and now have backups. Whether a hand-edited file still passes that check is not confirmed, so copy the file elsewhere first.

Related official history: patch 1.0.4 on 21 August 2026 banned special characters in server names because they broke the save file, and patch 1.0.6 changed saving to write on the Save, Main Menu and Quit buttons plus a one-minute autosave rather than on crash. Dates are on the patch notes page.

What is actually on the island

Very little is confirmed. The Steam guide ends at "enjoy exploring" without describing the place, and the mod README covers navigation and radar rather than content.

Claim	Status
The island scene exists in the shipped game	Confirmed by the DevIslandUnlocked README
It has baked lighting, meshes and colliders	Stated in the mod README
It has a SpawnManager, so creatures can spawn	Implied by the README's list of untouched components, not tested here
It has shops, NPCs or quests	Not confirmed yet
It holds unique fish or weapons	Not confirmed yet
It is part of any story route	Not confirmed yet, nothing in patch notes 1.0.4 to 1.0.11

Treat screenshots of "secret weapons" or "unused bosses" as unverified until a patch note or the developers confirm them.

Does it count for achievements?

Not confirmed. None of the game's 28 achievements, as listed in the community achievement guides, mentions a sixth island, and no patch note ties an achievement to one.

One sourced detail makes unique catches unlikely to matter: the post-game achievement guide was corrected to say the Collector achievement is driven by the lure you have equipped, not the island you stand on, so players can finish the encyclopedia from island five. If that holds, fishing off the developer island adds nothing the normal islands cannot. Player-tested, not a developer statement.

Be careful reading the developers' own numbering, too. Patch 1.0.11 mentions moving "the roulette table on island 6," while player guides put the roulette room on the volcano island they call island five. There is no confirmation that their "island 6" is the developer island. The islands and map page follows the numbering players use.

If you just want a new island to explore

Modded custom islands are the better documented alternative. CustomIslandsLoader (YoxiUI, 1.5.0, updated 1 September 2026) runs two kinds of map: replacement islands that stand in for one of the game's five and borrow its NPCs, shops and progression, and added islands, brand new places out in open water with their own radar colour, NPCs, shops and wildlife. Its README says added islands do not touch progression, need nothing unlocked, and never write to your save's island unlocks, which is the safety the save edit above lacks.

Rompedev's HTF Map Loader is the other loader in this space, with Rival Isles as its PvP-style reference arena. Both are covered on the custom islands mods page, and the wider picture is on best mods.

Sources and last check

Checked 2 September 2026. Mod facts, version numbers, downloads, dependency string, config path and the statement that DevIsland sits outside normal navigation come from the DevIslandUnlocked Thunderstore page by Rompedev; the custom island comparison from the CustomIslandsLoader page by YoxiUI. The save file location and the SpawnedIsland value of 5 come from the Steam Community guide "Secret Developer Island" and are player-reported: the save format is undocumented and may change in any patch. Official facts, the 1.0.5 fix for travelling to islands without unlocking them and the 1.0.11 save checks and island 6 roulette wording, come from the Dazed Games patch announcements on Steam. The Collector achievement being lure-driven is player-tested, from the community post-game achievement guide. Everything marked "not confirmed yet" had no source at this check.