diff --git a/biomes/swamp/marsh.json b/biomes/swamp/marsh.json
index c778f946..0f5d9502 100644
--- a/biomes/swamp/marsh.json
+++ b/biomes/swamp/marsh.json
@@ -10,6 +10,13 @@
         "max": 6,
         "generator": "mountain"
     }],
+    "customDerivitives": [{
+        "id": "swamp_marsh_rotten",
+        "waterColor": "#684D1A",
+        "grassColor": "#5C581A",
+        "spawnRarity": 20,
+        "spawns": [{"type": "SLIME"}]
+    }],
     "layers": [
         {
             "style": {"style": "IRIS"},