2

What I expected to happen was that the world would have lava sea and water sea.

What actually happened was that when i fly high up into the sky (like 100 block up), i'll see the background of the night time bellow the day texture and i'll see stars as black dots at day time.

Steps to Reproduce:
1. There you change your gamemode when creating a new world, press "More world options"
2. at "world type" press until it says "World type: Customized"
3. Press the button "Customise"
4. Turn on "lava oceans"
5. Press "Done" and then press "Create new world"