Since the changes to the underground began, the bottom of the oceanic biomes has been altered, some biomes such as the warm ocean have changed a lot compared to version 1.16.5, for example: the sand has been drastically decreased or replaced by stone around the biome, in other biomes it looks kinda weird compared with the ones generated in 1.16.5

How to reproduce this issue:

• Create a single biome with warm ocean or any other oceanic biome selected in 1.16.5 and fly
  around
• Create a single biome with the same preset you choiced in 1.16.5 but in 21w13a and fly
  around

You will notice that the ocean generation looks different (in the case of warm ocean it looks worse)