Changes since 1.21.5 release:

• Reverted back to stock world generation: Added back top layer of ice in most snowy/frozen biomes to make it easier for the player to navigate
• Added Underwater Potion to most village chests that grants the player 30 minutes of water breathing upon drinking
• Corals, budding amethyst, ice variants, mushroom blocks can be mined with simple tools without silk touch enchantment
• Reverse crafting ice, corals, mushroom blocks via crafting table or stonecutter is now possible
• Safe world spawn is still risky. Since I'm still horrible at coding and couldn't come up with a fix platform generation during the first time the player spawns in the world, I'll give you pre-tested seeds that have safe world spawn:

• Spawn on ice: 906182347964544722
  

• Spawn on abandoned ship: 6696165159819216322
  

• Spawn on a floating nether portal: 2589681248334255595