minecraft-assets/data/minecraft/recipes/sea_lantern.json

{
  "type": "minecraft:crafting_shaped",
  "category": "building",
  "key": {
    "C": {
      "item": "minecraft:prismarine_crystals"
    },
    "S": {
      "item": "minecraft:prismarine_shard"
    }
  },
  "pattern": [
    "SCS",
    "CCC",
    "SCS"
  ],
  "result": {
    "item": "minecraft:sea_lantern"
  }
}