diff --git a/backend/routers/water.py b/backend/routers/water.py
index 3b4fe5e..df3ae16 100644
--- a/backend/routers/water.py
+++ b/backend/routers/water.py
@@ -165,19 +165,23 @@ def _water_geoms(elements: list[dict]) -> list[dict]:
                 poly = _way_to_polygon({'geometry': mg})
                 if poly is None:
                     continue
-                polygons.append(poly['coordinates'][0])
+                # Кладём Polygon целиком (coordinates = [ring]), не сам ring —
+                # иначе у одиночного кольца coordinates получатся depth-2.
+                polygons.append(poly['coordinates'])
                 area, lat, lon = _polygon_centroid_area(mg)
                 areas.append(area)
                 lats.append(lat)
                 lons.append(lon)
             if not polygons:
                 continue
-            geom = (
-                # GeoJSON MultiPolygon: [[ring0], [ring1]] — каждый полигон = список колец.
-                {'type': 'MultiPolygon', 'coordinates': [[p] for p in polygons]}
-                if len(polygons) > 1 else
-                {'type': 'Polygon', 'coordinates': polygons[0]}
-            )
+            if len(polygons) == 1:
+                geom = polygons[0]  # {'type': 'Polygon', 'coordinates': [ring]}
+            else:
+                # GeoJSON MultiPolygon: собираем полигоны в один Multi.
+                geom = {
+                    'type': 'MultiPolygon',
+                    'coordinates': [p['coordinates'] for p in polygons],
+                }
             out.append({'layer': layer, 'name': name, 'geom': geom,
                         'area_m2': sum(areas),
                         'lat': sum(lats) / len(lats), 'lon': sum(lons) / len(lons)})