Published: March 29, 2026 
The latest Fish It update added a brand new fishing spot called the Sewers. It was hiding in plain sight the whole time, tucked inside a cave in the Underwater City that used to be completely blocked off. Now that it's open, you can head in and fish for some new catches, including a secret fish that looks like it came straight out of a nuclear disaster. In this Fish It Sewers guide, I will show you everything you need to know about it and how to get the new Bonemaw Tyrant inside.
How to Unlock the Sewers in Fish It
If you want to visit this new POI, you just need to head to the Underwater City and make your way to the cave in front of the Duck Boy NPC. Before the update, this cave was sealed shut and easy to ignore. Now the entrance is open, and walking through it takes you straight into the Sewers.
Once you're inside, you'll find two spots where you can cast your line. The area has a dark, grungy feel to it, which fits the radioactive theme of the fish you'll find there. The Sewers have five new fish you can catch, and most of them overlap with what you'd already find in the Underwater City. A handful are unique to this spot, but the real reason to come here is the secret fish.
What's Inside the Sewers
Before you start fishing in the Sewers, you'll want to pick up the Radioactive Charm. This charm is available in the Sewers area, costs 20,000 coins, and it does one thing: it increases your chance of getting a radioactive mutation by 1.3x.
If you're someone who likes collecting mutated fish, this charm is worth grabbing. It doesn't affect your catch rate for regular fish, but that extra push toward radioactive mutations can help if you are grinding for rare variants.
How to Get Bonemaw Tyrant in Fish It Sewers
The star of the Sewers is the Bonemaw Tyrant. This is the secret fish for the Sewers location, and catching one is going to take some patience. Here's what you need to know about it:
| Stat | Detail |
|---|---|
| Fish Type | Secret |
| Location | Sewers (Underwater City) |
| Max Weight | ~220 kg |
| Average Weight | ~150 kg |
| Theme | Radioactive / mutated |
Size-wise, the Bonemaw Tyrant is on the smaller end compared to other secret fish in the game. It maxes out at around 220 kg, with most catches landing closer to 150 kg.
Getting the Bonemaw Tyrant isn't guaranteed, but there are a few things you can do to improve your chances.
- Equip the Radioactive Charm before you start fishing. It won't directly increase Bonemaw Tyrant's spawn rate, but leaning into the radioactive theme of this area is good when you're hunting this fish.
- Fish during Bloodmoon events if you can. The first known Bonemaw Tyrant catch happened during a Blood Moon, so timing your session around one could help.
- Try both fishing spots inside the Sewers. There are two casting locations, and it's worth rotating between them if one isn't producing results.
If you're a completionist trying to fill out your fish index, the Sewers need to be on your list. And if you're hunting for that Bonemaw Tyrant, get the Radioactive Charm ready and keep casting. For more codes, tips, and info about this game, you can always check our dedicated Fish It wiki.
