Build an Underwater Level in Unity: Swimming Controller, FX, Vegetation & Terrain (Free Tools)

Explore how to build a complete underwater level in Unity, including a custom swimming controller, realistic underwater effects, animated sea plants, and terrain setup.

In this full 20-minute deep dive, I walk through every step of creating an immersive underwater experience: from player movement to environmental FX and share two free UPM packages you can install to follow along easily.

🌊 What You’ll Learn

✅ How to create a swimming controller with smooth vertical movement
✅ Setting up underwater fog, bubbles, and lighting effects
✅ Building the sea floor terrain with realistic textures
✅ Adding animated vegetation using my Unity tool
✅ Tips for water surface visuals and post-processing
✅ Installing and using custom UPM packages

🧰 Tools Used

Unity (URP)
Codex CLI – code generation for controller logic
Rodin / Hyper3D – asset & plant generation
3DAI Studio – optional for props or creatures
Custom UPM packages (linked below)

📦 Free Packages
🌀 Swimming Controller – adds full 3D swim movement
https://github.com/mdj128/yt-underwat...
🌿 Animated Vegetation Importer – convert static plants into animated terrain details
https://github.com/mdj128/yt-underwat...
GitHub: https://github.com/mdj128/yt-underwat...

⏱️ Timestamps

0:00 Intro
0:27 Swim controller
4:11 Underwater visual effect
4:30 terrain and textures
7:11 Underwater sea plants
14:25 Terrain detail importer
15:46 Water surface
17:38 Terrain detail painting
18:48 Adding underwater bubbles & FX
21:15 Outro

If you enjoy this, check out my previous Unity tools:
🔥 Lava Cave Level Tutorial:    • 3D Unity AI Game Dev Tutorial (Beginner Fr...  
📦 AI Game Dev series:    • AI Generated Character in Unity? Full 3D G...  

I’m working on a combat-ready character controller next — subscribe if you want to see that in action! ⚔️