SpeedyMouse's Lost River Challenge
⚪ Last updated 2022⚠️ Install Order · 2 steps
Install in this order, then this mod last — most mods fail to load without their framework and dependencies in place.
Preview

🔍 Analysis
- 👍 3.2% endorsement rate — high engagement, a strong quality signal
- 🏆 #65 of 126 Adventure mods in this game by downloads
📋 About This Mod
Soon after Ryley Robinson’s return to Alterra, several research teams are sent to 4546B to catalog the species there and begin to uncover alien technology left by the Precursors. During one research mission, you and your team are sent to explore the Lost River. However, not far along into the expedition, your team is attacked by a Ghost Leviathan. You manage to escape in a SeaMoth just before the Cyclops explodes, although it’s damaged by the blast. Disoriented, you travel deeper into the depths of the Lost River, until you finally stop where we find you now. You decide to get out and quickly construct a base for shelter, hoping to have a safe place to recuperate and decide what to do next. However, moments after you finish the base’s construction, a River Prowler attacks, destroying your SeaMoth, and knocking your Habitat Builder into the brine…
This save file starts you in the Lost River Junction with a base and a small number of resources in a locker. Your goal is to make it to the surface alive. Once you reach the surface, the challenge is complete. From there, you can complete the game as you normally would, if you wish.
If you get stuck, you can watch this video to get yourself going in the right direction: https://youtu.be/ie3Mze-ctWA
This save file is a companion to "SpeedyMouse's Lava Zone Challenge."
This save file is heavily inspired by GreyMtnFox's Lost River Survival Challenge. I used that file in my YouTube video, but decided to slightly modify the rules of the challenge, hence this upload. If you want to check out his original challenge, here's the link: https://www.nexusmods.com/subnautica/mods/912
No mods are required to run this file.
Installation:
Copy this world file into your "SavedGames" folder for Subnautica. This folder is found in several different locations depending on what platform you play the game on. A quick google search can help you find it or you can always just search for it on your computer.
SpeedyMouse's Lost River Challenge is a compact adventure mod that strands players in the Lost River with limited resources, testing survival skills. With 21 endorsements and 654 downloads, it's a niche challenge for players seeking a focused survival experience.
✨ Key Features
📊 Pros & Cons
✅ Pros
- Tight survival premise that strips away excess and forces creative thinking
- Small but dedicated following (21 endorsements) suggests it delivers for its niche
- Lightweight mod that doesn't overhaul the game—just drops you in and lets you figure it out
⚠️ Cons
- Last updated in April 2022—might not be compatible with the latest game version
- Limited scope means once you've beaten it, there's little replay value
For survival purists who want a self-contained challenge without mod bloat. If you're looking for a quick, focused test of your resourcefulness, this is a good pick. Skip if you want a sprawling adventure or need hand-holding.
💡 Beginner Tips
- Scavenge everything early—resources are scarce and you'll need to stretch them
- Plan your route before moving; the Lost River can be disorienting
- Check the mod's comments section for any known issues or player tips
📊 Mod Details
- Game
- Subnautica Mods
- Author
- SpeedyMouse
- Version
- 1.0
- Downloads
- 654
- Endorsements
- 21
- Category
- Adventure
- Created
- 4/15/2022
- Updated
- 4/15/2022
🔧 How to Install Subnautica Mods
Download from Nexus.
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