{
    "feature": "minecraft:underwater_magma",
    "placement": [
        {
            "type": "minecraft:count",
            "count": {
                "type": "minecraft:uniform",
                "min_inclusive": 250,
                "max_inclusive": 255
            }
        },
        {
            "type": "minecraft:height_range",
            "height": {
                "type": "minecraft:uniform",
                "min_inclusive": {
                    "above_bottom": 0
                },
                "max_inclusive": {
                    "absolute": 256
                }
            }
        },
        {
            "type": "minecraft:in_square"
        },
        {
            "type": "minecraft:surface_relative_threshold_filter",
            "heightmap": "OCEAN_FLOOR_WG",
            "max_inclusive": -5
        },
        {
            "type": "minecraft:biome"
        }
    ]
}