It is an unofficial port. Nothing changed, just updated to 1.21. hibi's 1.20 version
hibi's description:
Boat Hud
A Fabric mod that adds a HUD specifically for boating. Licensed under Unlicense.

This HUD displays some information useful for boating such as drift angle and speed.
This mod needs Cloth Config. To configure, you need Mod Menu.
How to Install BoatHud for 1.21 (hibi's) (Mod)
BoatHud for 1.21 (hibi's) by jewtvet is verified for Fabric across Minecraft versions 1.21 (latest release: 1.2.1, file size: 21 KB). Follow the steps below to install it safely from ModCraft.tv:
- Click the Download button above and select your Minecraft version (1.21) and platform (Fabric).
- Make sure you have the compatible loader or environment installed for Fabric.
- Move the downloaded BoatHud for 1.21 (hibi's) file into your Minecraft
.minecraft/modsfolder and launch the game.
All Versions
+ Add Version- AD keystokes were added to compact mode ([Sotumney's code for 1.20](https://github.com/Sotumney/BoatHudCompact/tree/main))
- Ported to 1.21