Swim Fix
by ENC_Euphony
Swim Fix addresses Minecraft bug MC-220390, where a player who swims underwater can stop swimming, become trapped in open water or be blocked by a nearby block.
What it does
The bug comes from the player's hitbox changing size while swimming underwater. A player hit by an entity can stop swimming for a brief moment, and a large hitbox can collide with a block even when a smaller one would fit. Swim Fix corrects the swimming logic so a player can return to swimming and move below a block without getting stuck.
Installation is needed on the server only, since the environment is server-side only and players join without installing anything. Swim Fix is published for Fabric and NeoForge across 11 release versions, with 1.1.0 as the latest file for 1.21.10. It is open source under the GNU Lesser General Public License v3.0 only, and its source code is public.
Key features
Swimming resumes after hits
A player hit by an entity while underwater continues swimming instead of stopping for a moment.
Fixes for stuck swimmers
A player caught in the middle of the water can swim again and move below a block that was blocking them.
Hitbox collision correction
Collisions use the correct hitbox while swimming, so a larger hitbox no longer catches on blocks a smaller one passes.
Architectury base
The mod is built on Architectury, which lets one codebase serve both Fabric and NeoForge.
Compatibility
Latest build for each game version and loader.
1.21.x11 of 11 versions with builds
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Servers with aquatic builds
Server owners with underwater bases, tunnels or water-based areas can install the fix so players are not held up by the swimming bug.
Players exploring oceans
Players who travel through open water on a server get consistent swimming when fights or terrain interrupt them.
Who it’s for: Server owners running Fabric or NeoForge who want players to swim without the MC-220390 bug. Players only need the server-side install, so client setups are unaffected.
How it compares
Projectile Fix is a Fabric and NeoForge mod for 1.21 – 1.21.8, client and server, and is open source under the MIT License. Only Elytra Hitbox is a Fabric-only client mod for 1.21.1 – 1.21.11, released under CC0 1.0 Universal and not open source. Swim Fix is server-side only, targets Fabric and NeoForge, and is open source under the GNU Lesser General Public License v3.0 only.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Swim Fix | Fabric and NeoForge | 1.21 – 1.21.10 | Server-side only | 2025-11-20 |
| Projectile Fix | Fabric and NeoForge | 1.21 – 1.21.8 | Client and server | 2025-09-01 |
| Only Elytra Hitbox | Fabric | 1.21.1 – 1.21.11 | Client-side only | 2025-12-29 |
Questions
Does Swim Fix need to be installed on the client?
Which loaders does Swim Fix support?
Does Swim Fix work with a server on 1.21.11?
In the catalog
Swim Fix is one of 3,545 Optimization mods on ModsFinder, and one of 2,575 Optimization mods for Fabric. 15,569 mods support Minecraft 1.21.10.
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What the author says
An Architectury mod that fixes Minecraft bug MC-220390 for swimming in water. If you hit an entity while swimming underwater, the player will stop swimming for a brief moment (it changes the size of its hitbox and returns to the swimming one) and then get stuck in the middle of the water if they try to swim below a…
Official listing
- Modrinth page
- modrinth.com/mod/swim-fix
- Owner
- ENC_Euphony
- Published
- 2025-11-20
- Updated on Modrinth
- 2025-11-20
- Facts verified
- 2026-10-15