If you've been scratching your head over how to make a swimming system script, you probably already know that water physics can be one of the trickiest parts of game dev to get right. It's not just about turning off gravity and calling it a day; you have to make the player feel like they're actually moving through a dense fluid rather than just flying through the air in slow motion.
Whether you're working in Unity, Roblox, or Godot, the logic behind a solid swimming system stays pretty much the same. You need to detect when the player hits the water, change how they move, and—most importantly—make sure they can actually get back out of the pool without getting stuck on the edge. Let's break down how to actually build this thing from the ground up without overcomplicating it.
Setting up the water detection
Before you even touch your movement code, you need a way for your script to know the player is actually in the water. Most people use a trigger volume for this. Think of it as an invisible box that sits exactly where your water is.
When the player's character enters that box, the script fires off a signal saying, "Hey, we're wet now!" and when they leave, it says, "Okay, back to land." In your script, you'll usually use something like an OnTriggerEnter or onPartTouched function.
The biggest mistake I see beginners make is forgeting to check what entered the water. You don't want the water logic to trigger because a random prop fell in. You need to make sure the script checks for a "Player" tag or a specific component. Once you've confirmed it's the player, you can flip a boolean variable—let's call it isSwimming—to true.
Changing the physics and gravity
The core of figuring out how to make a swimming system script is the physics shift. In most game engines, "walking" mode has high friction on the ground and constant downward gravity. Swimming is different. You want to significantly reduce gravity—or even turn it off entirely—and replace it with something that feels more like buoyancy.
Instead of a hard fall, you want the player to slowly drift. You can do this by applying a constant upward force whenever the player is submerged. If the upward force equals the downward force of gravity, the player just floats. If you want them to slowly sink, keep the gravity a little bit stronger than the buoyancy.
Don't forget about drag. Water is heavy. When the player stops pressing the "W" key, they shouldn't just slide forever like they're on ice. You need to crank up the linear drag in your physics component as soon as isSwimming becomes true. This gives that "thick" feeling where movement feels intentional and requires effort.
Handling 3D movement and verticality
On land, your player usually moves on the X and Z axes (left, right, forward, back). In the water, you suddenly have to deal with the Y-axis. There are two main ways to handle this in your script, and the one you choose depends on the "vibe" of your game.
Looking where you swim
The most common way is to make the player move in whatever direction the camera is pointing. If they look down and press forward, they dive. If they look up, they surface. This is usually the most intuitive for players. To script this, you'd take the camera's forward vector and multiply it by your swimming speed.
Manual vertical controls
The other way is to keep forward movement strictly horizontal and use specific keys (like Space to go up and C or Shift to go down). This feels a bit more "old school" or simulation-heavy. If you're making a deep-sea exploration game, this might be the better way to go because it gives the player more precise control over their depth.
Smooth transitions and animations
A script can have perfect math and still feel like garbage if the visuals don't match. You've got to handle the transition between the "Idle" or "Running" animations and the "Swimming" ones.
When isSwimming hits true, you should tell your animation controller to switch states. But here's a pro tip: use proportional animation speeds. If the player is barely moving, the swim stroke should be slow. If they're sprinting (or "fast swimming"), the animation should speed up. It's a small detail, but it makes the script feel way more professional.
Also, think about the "treading water" state. When the player is just floating there, you want a subtle, bobbing animation. You can actually code this into the script by adding a tiny sine wave movement to the player's Y-position. It keeps the character from looking like a frozen statue while they're waiting for you to move the mouse.
Getting out of the water
This is honestly the hardest part of learning how to make a swimming system script. We've all played those games where you swim to the edge of a pool but just bump your head against the curb because you can't "step" up onto the land.
You need a "mantle" or "climb" check. You can do this by casting a short raycast (an invisible line) forward from the player's chest. If the raycast hits a wall while the player is swimming, you check if there's empty space above that wall. If there is, you temporarily disable the swimming physics and "pop" the player up onto the ledge.
Without this bit of logic, your swimming system will feel like a trap. Players hate feeling stuck, so spend some extra time making the transition from water to land feel snappy.
Adding the "Drowning" logic
Unless your main character is a mermaid or a robot, they probably need to breathe. Adding an oxygen bar is a great way to add tension.
Inside your swimming script, you can set up a timer. If the player's head (which you can track with another small trigger or a position check) goes below the water level, start a countdown. If that countdown hits zero, you start docking health points every second.
Make sure to reset that timer the instant their head clears the surface. There's nothing more frustrating than dying because the game didn't realize you were already gasping for air.
Polishing the experience with sound and VFX
Technically, this isn't "scripting" movement, but it is part of the system's script logic. You should trigger sound effects and particles based on the player's velocity.
- Splashes: If the player hits the water at high speed, trigger a "Splash" particle effect and a loud sound.
- Bubbles: While submerged, emit a few bubble particles from the player's mouth area.
- Underwater Audio: Use an audio filter (like a low-pass filter) to muffle all the game's sounds as soon as the camera goes underwater.
These little touches are what separate a "basic" script from a "system." It tells the player's brain, "Okay, we are definitely in a different environment now."
Testing and common bugs
Once you've got your script running, you're going to find some weird bugs. It's just part of the process. One common issue is "jittering" at the surface. This happens when the script can't decide if the player is in or out of the water, so it keeps toggling the gravity on and off.
To fix this, use a buffer zone (often called hysteresis). Instead of having one exact line where swimming starts, have a small overlap where the player is considered "swimming" until they are significantly above the water line.
Another one is the "infinite jump" bug. If your game lets players jump out of the water, make sure they can only do it when they're near the surface. Otherwise, they might be able to "jump" through the water like a dolphin on caffeine, which is funny, but probably not what you're going for.
Learning how to make a swimming system script takes some trial and error, but it's really rewarding once you get that smooth, buoyant feel. Just take it one step at a time—start with the detection, move to the physics, and then finish with the polish. Before you know it, you'll have a character that's just as comfortable in the deep end as they are on solid ground.