You can breathe indefinitely underwater by filling and emptying buckets or by playing blocks that can be placed in water and replaced by water

The bug

This bug allows you to breathe underwater for an unlimited amount of time by repeatedly using the bucket in the same space as your head. This allows you to gain air or oxygen with some time and you can repeat this process multiple times to get a continuous supply of air.

How to Reproduce

1. Be in survival and go underwater
2. Wait a little bit until some of your air bubbles disappeared
3. aim at a bock next to your head and hold down right click while holding a bucket
   → Your air meter refills