Beta 188.8.131.52 adds the colorful axolotl mob, which has been in Java Edition for several months.
Axolotls spawn in flooded caves underground and come in five different varieties, including the super rare blue axolotl.
You can pick up an axolotl using a bucket. When damaged, an axolotl will 'play dead' while it regenerates.
Additionally, deepslate has been added, which generates at the bottom of the world, replacing stone.
Deepslate comes in a cobbled variant, dropped when it is mined. Cobbled deepslate can then be polished, chiseled, or turned into bricks or tiles.
All ores now come in deepslate variants, which can be found embedded within deepslate. These ores take longer to mine but otherwise act exactly the same as regular ores.
Copper can now be waxed with an axe by a player. This applies to but oxidised copper and cut oxidised copper.
This beta is available for Android, Xbox, and Windows 10 for users in the beta program.