Here is a screenshot showing water in both 1.15 & 1.16. They use the exact same code (the formatting was updated from 1.15's biome file to 1.16) however, they have completely different results. I would consider this a pretty drastic bug, especially for Marketplace related content, as custom water colours can really help sell the vibe of a creation.

JSON Snippet used:

{
  "biomes": {
    "default": {
      "water_surface_color": "#15FFFF",
      "water_surface_transparency": 0.45,
      "water_fog_color": "#0B1C33",
      "water_fog_distance": 350
    }
  }
}

Please could you fix this?