Minecraft 1.12.2
Forge 14.23.5.2847
Metamorph 1.1.10-1.12.2 (or Changeling equivalent)
Classic Bar 0.5.4
See Tfarcenim/ClassicBar#53

When morphed as a Squid and out of water, the air meter displayed is the Minecraft default and not the one from Classic Bar, which is inconsistent.

To Reproduce:

1. Install the aforementioned mods.
2. Be underwater. Notice the air meter displayed is the one from Classic Bar.
3. Morph to a Squid. Notice the air meter disappears as it should (you can only breathe underwater).
4. Jump out of water. Notice the air meter displayed is the Minecraft default and not the one from Classic Bar.

Per Tfarcenim/ClassicBar#53 the issue would have to be fixed on Changeling's end. It may be possible to fix this by temporarily changing the player's air stat, however this may have unintended consequences that need to be taken into account. I also don't personally feel like working on this.

Yeah, I have no interest of working on it either.