There is sometimes an additional 11th bubble in survival/adventure mode

Occasionally, after going out of the water to take a breath, an eleventh bubble appears on the oxygen meter for a short time.

How to Reproduce

• Get a turtle shell (easier to reproduce) and wear it

• Go to a body of water deep enough to decrease your oxygen level

• Run the following commands:
  /scoreboard objectives add air air Air
/scoreboard objectives setdisplay sidebar air

• Decrease your oxygen level then go back up the surface to fully recover your oxygen

Occasionally, it appears. Sometimes, it won't. The eleventh bubble is likely to be cause by the air level to exceed 300 and go up to 303.

• Air level 303 makes the eleventh bubble appear

• Air level 302-301 makes the eleventh bubble's popping animation