minecraft_server_zombie/config/alexsmobs/seal_spawns.json

{
  "biomes": [
    [
      {
        "type": "BIOME_DICT",
        "negate": false,
        "value": "overworld"
      },
      {
        "type": "BIOME_DICT",
        "negate": false,
        "value": "beach"
      }
    ],
    [
      {
        "type": "BIOME_DICT",
        "negate": false,
        "value": "overworld"
      },
      {
        "type": "BIOME_DICT",
        "negate": false,
        "value": "ocean"
      },
      {
        "type": "BIOME_DICT",
        "negate": false,
        "value": "snowy"
      }
    ],
    [
      {
        "type": "REGISTRY_NAME",
        "negate": false,
        "value": "terralith:gravel_beach"
      }
    ]
  ]
}