Deep Fishing Mutations Guide: Effects, Value, and How to Get Mutated Fish

Quick answer

Mutations in Deep Fishing are a separate collection layered on top of a catch — a value modifier rather than a rarity of their own. A mutation is not a fourth named rarity above Secret and not a replacement for Legendary: it modifies the catch you already landed, so a mutated Common is still not a Secret.

• Diamond is the only mutation type documented by name; other catches are seen to 'turn mutated' (squid, toxic fish, shark, clownfish) without their mutation names shown.
• Mutated fish come from far-water grinding, Mutation Scroll pickups on long casts, and the 349-Robux More Mutations gamepass.
• Keep your first mutated catch for the First Mutation badge, and turn Auto Sell off until that badge is unlocked.

What mutations are (and why they are not a rarity rank)

Mutations sit on top of whatever rank you already landed. They modify the catch you already have, so a mutation does not promote a Common into a Secret — a mutated Common is still not a Secret. What a mutation changes is that the same rank becomes more interesting, more collectible, and often more valuable when sold, which is why the First Mutation badge is a separate trophy from First Legendary. Treat mutations as a value modifier on each live catch you sell rather than as part of the Common/Legendary/Mythical/Secret rarity ladder.

Documented mutation types: Diamond

Diamond is the only mutation type explicitly named in documented gameplay. In one recorded session, the creator lands catches described as "legendary diamond" and remarks, "Diamond mutations. I like that." The same footage shows other catches that "turn mutated" — a squid, a toxic fish, a mutated shark, and a mutated Nemo/clownfish variant — without naming their mutation types. A complete official mutation list with names, odds, or per-mutation effects has not been published, so treat any longer list circulating elsewhere as unconfirmed.

What mutations change: observed sale values

Observed mutated catches and their reported sale values, from a single creator session:

Comparison

Comparison

Observed Catch	Reported Value	Session Note
-	-	-
-	-	-
-	-	-

These prices come from a boosted admin-event session — 4x luck, event weather (rain, toxic, thunder), and a Double Coins purchase during the video — so they illustrate the value effect rather than establish baseline multipliers, and no per-mutation multipliers have been published. At the system level: a mutated Common can be worth holding for the First Mutation badge, a mutated Legendary is a coin spike, and a mutated Mythical or Secret is the kind of inventory you screenshot before you sell. As the session's creator puts it: once you get the good mutation, that's when the real money comes in.

How to get mutated fish

Checklist

• Grind far water

  Far water is where Legendary, Mythical, Secret, and mutated fish live, and catches are observed to 'turn mutated' as they are landed. Grinding farther water is the free route.

• Hook Mutation Scroll pickups on long casts

  Long casts can hook a Mutation Scroll like loot: a bait table lists 'High-value fish, Mutation Scroll' as results on a Bronze Rod + Meadow Bait cast at 500+ m, and gameplay shows a scroll pulled from a haul. The scroll's exact effect when used — what it targets, its success chance, its mutation pool — is not documented yet.

• Buy the More Mutations gamepass

  The paid increase to mutated finds, covered in detail below.

Mutation odds are not published for any of these routes, so treat any percentage you see elsewhere as unconfirmed.

First Mutation badge

First Mutation is its own progression badge, separate from First Legendary — the game treats the first mutated catch as a milestone. Rolimon's badge data (September 2026) lists First Mutation with a 100.0% win rate and 902,345 awards, making it one of the game's most widely earned trophies. Because the badge is tied to the first mutated catch, session guides say to keep it: keep the first Legendary, the first Mythical, the first Secret, and the first Mutation for badges, and sell Commons unless a mutation is sitting on one you still need for First Mutation or a variant you care about.

More Mutations gamepass: cost and when it is worth it

The paid lever for the mutation system is the More Mutations gamepass, priced at 349 Robux as of September 2026. Its official description is "Find more mutated Fishes!" and it is described as the official tilt for mutation rolls. It is a collector purchase with a job the luck stack does not copy: luck passes may help you see rarer base ranks, but they are not the same purchase — More Mutations does not replace luck and does not replace Strength, and no exact mutation-rate figure has been published for it. It is worth buying when First Mutation or variant collecting is the goal; if you only want coins, skip it and keep selling.

Auto Sell and inventory handling while hunting mutations

Tips

Turn Auto Sell off while badge hunting

Keep it off until First Mutation is unlocked (alongside First Legendary, First Mythical, and First Secret), while you are collecting mutations on purpose, and while checking labels after a far cast.

Switch it back on for volume selling

Once the badge is done and you are back to volume selling, turn Auto Sell on again.

Never assume Auto Sell knows your badge goals

A mutated Secret is the kind of haul you do not Auto Sell by accident.

Read the label before the inventory clears

Auto Sell does not pay off if you cannot recognize a mutation — reading the mutated label on a catch before the inventory clears is part of the skill.

A September promo code pays bait, not mutations

One September 2026 code list includes a promo code named after the mutation system — and despite the name, it redeems 5 Meadow Bait: bait supplies for casting, not a mutation itself. To redeem, open the Shop window and scroll to the bottom, where codes are redeemed, then paste the string exactly with no extra spaces. Code lists currently disagree on September 2026 Deep Fishing codes — that list shows the entry as working, while other sources report no confirmed codes that month — so treat availability as unconfirmed until it redeems in your game; the current codes guide tracks the strings with broader agreement.

Prices, badge award counts, and code status on this page are September 2026 snapshots — recheck them after game updates.