diff --git a/apps/web/src/app/styles.css b/apps/web/src/app/styles.css
index 1037b54..3d864f8 100644
--- a/apps/web/src/app/styles.css
+++ b/apps/web/src/app/styles.css
@@ -971,7 +971,7 @@ body {
 }
 
 .map-settings-panel .ms-title {
-  font-size: 10px;
+  font-size: 11px;
   font-weight: 700;
   color: var(--text);
   letter-spacing: 1px;
@@ -983,11 +983,11 @@ body {
 }
 
 .map-settings-panel .ms-label {
-  font-size: 8px;
-  font-weight: 700;
-  color: var(--muted);
-  letter-spacing: 1px;
-  margin-bottom: 4px;
+  font-size: 10px;
+  font-weight: 600;
+  color: var(--text);
+  letter-spacing: 0.5px;
+  margin-bottom: 5px;
 }
 
 .map-settings-panel .ms-row {
@@ -1019,12 +1019,12 @@ body {
 
 .map-settings-panel .ms-hex {
   font-size: 9px;
-  color: var(--muted);
+  color: #94a3b8;
   font-family: monospace;
 }
 
 .map-settings-panel .ms-depth-label {
-  font-size: 9px;
+  font-size: 10px;
   color: var(--text);
   min-width: 48px;
   text-align: right;
diff --git a/apps/web/src/features/mapSettings/MapSettingsPanel.tsx b/apps/web/src/features/mapSettings/MapSettingsPanel.tsx
index f7dc386..592fb60 100644
--- a/apps/web/src/features/mapSettings/MapSettingsPanel.tsx
+++ b/apps/web/src/features/mapSettings/MapSettingsPanel.tsx
@@ -1,5 +1,5 @@
 import { useState } from 'react';
-import type { MapStyleSettings, MapLabelLanguage, DepthFontSize } from './types';
+import type { MapStyleSettings, MapLabelLanguage, DepthFontSize, DepthColorStop } from './types';
 import { DEFAULT_MAP_STYLE_SETTINGS } from './types';
 
 interface MapSettingsPanelProps {
@@ -25,8 +25,42 @@ function depthLabel(depth: number): string {
   return `${Math.abs(depth).toLocaleString()}m`;
 }
 
+function hexToRgb(hex: string): [number, number, number] {
+  return [
+    parseInt(hex.slice(1, 3), 16),
+    parseInt(hex.slice(3, 5), 16),
+    parseInt(hex.slice(5, 7), 16),
+  ];
+}
+
+function rgbToHex(r: number, g: number, b: number): string {
+  return `#${[r, g, b].map((c) => Math.round(Math.max(0, Math.min(255, c))).toString(16).padStart(2, '0')).join('')}`;
+}
+
+function interpolateGradient(stops: DepthColorStop[]): DepthColorStop[] {
+  if (stops.length < 2) return stops;
+  const sorted = [...stops].sort((a, b) => a.depth - b.depth);
+  const first = sorted[0];
+  const last = sorted[sorted.length - 1];
+  const [r1, g1, b1] = hexToRgb(first.color);
+  const [r2, g2, b2] = hexToRgb(last.color);
+  return sorted.map((stop, i) => {
+    if (i === 0 || i === sorted.length - 1) return stop;
+    const t = i / (sorted.length - 1);
+    return {
+      depth: stop.depth,
+      color: rgbToHex(
+        r1 + (r2 - r1) * t,
+        g1 + (g2 - g1) * t,
+        b1 + (b2 - b1) * t,
+      ),
+    };
+  });
+}
+
 export function MapSettingsPanel({ value, onChange }: MapSettingsPanelProps) {
   const [open, setOpen] = useState(false);
+  const [autoGradient, setAutoGradient] = useState(false);
 
   const update = <K extends keyof MapStyleSettings>(key: K, val: MapStyleSettings[K]) => {
     onChange({ ...value, [key]: val });
@@ -34,7 +68,19 @@ export function MapSettingsPanel({ value, onChange }: MapSettingsPanelProps) {
 
   const updateDepthStop = (index: number, color: string) => {
     const next = value.depthStops.map((s, i) => (i === index ? { ...s, color } : s));
-    update('depthStops', next);
+    if (autoGradient && (index === 0 || index === next.length - 1)) {
+      update('depthStops', interpolateGradient(next));
+    } else {
+      update('depthStops', next);
+    }
+  };
+
+  const toggleAutoGradient = () => {
+    const next = !autoGradient;
+    setAutoGradient(next);
+    if (next) {
+      update('depthStops', interpolateGradient(value.depthStops));
+    }
   };
 
   return (
@@ -97,19 +143,34 @@ export function MapSettingsPanel({ value, onChange }: MapSettingsPanelProps) {
 
           {/* ── Depth gradient ────────────────────────────── */}
           <div className="ms-section">
-            <div className="ms-label">수심 구간 색상</div>
-            {value.depthStops.map((stop, i) => (
-              <div className="ms-row" key={stop.depth}>
-                <span className="ms-depth-label">{depthLabel(stop.depth)}</span>
-                <input
-                  type="color"
-                  className="ms-color-input"
-                  value={stop.color}
-                  onChange={(e) => updateDepthStop(i, e.target.value)}
-                />
-                <span className="ms-hex">{stop.color}</span>
-              </div>
-            ))}
+            <div className="ms-label" style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between' }}>
+              수심 구간 색상
+              <span
+                className={`tog-btn${autoGradient ? ' on' : ''}`}
+                style={{ fontSize: 8, padding: '1px 5px', marginLeft: 8 }}
+                onClick={toggleAutoGradient}
+                title="최소/최대 색상 기준으로 중간 구간을 자동 보간합니다"
+              >
+                자동채우기
+              </span>
+            </div>
+            {value.depthStops.map((stop, i) => {
+              const isEdge = i === 0 || i === value.depthStops.length - 1;
+              const dimmed = autoGradient && !isEdge;
+              return (
+                <div className="ms-row" key={stop.depth} style={dimmed ? { opacity: 0.5 } : undefined}>
+                  <span className="ms-depth-label">{depthLabel(stop.depth)}</span>
+                  <input
+                    type="color"
+                    className="ms-color-input"
+                    value={stop.color}
+                    onChange={(e) => updateDepthStop(i, e.target.value)}
+                    disabled={dimmed}
+                  />
+                  <span className="ms-hex">{stop.color}</span>
+                </div>
+              );
+            })}
           </div>
 
           {/* ── Depth font size ───────────────────────────── */}
@@ -146,7 +207,10 @@ export function MapSettingsPanel({ value, onChange }: MapSettingsPanelProps) {
           <button
             className="ms-reset"
             type="button"
-            onClick={() => onChange(DEFAULT_MAP_STYLE_SETTINGS)}
+            onClick={() => {
+              onChange(DEFAULT_MAP_STYLE_SETTINGS);
+              setAutoGradient(false);
+            }}
           >
             초기화
           </button>
diff --git a/apps/web/src/widgets/map3d/hooks/useMapStyleSettings.ts b/apps/web/src/widgets/map3d/hooks/useMapStyleSettings.ts
index 1f6fece..2cf0724 100644
--- a/apps/web/src/widgets/map3d/hooks/useMapStyleSettings.ts
+++ b/apps/web/src/widgets/map3d/hooks/useMapStyleSettings.ts
@@ -51,14 +51,21 @@ function applyLabelLanguage(map: maplibregl.Map, lang: MapLabelLanguage) {
 function applyLandColor(map: maplibregl.Map, color: string) {
   const style = map.getStyle();
   if (!style?.layers) return;
-  const landRegex = /(land|landcover|landuse|earth|continent|terrain|park)/i;
+  const waterRegex = /(water|sea|ocean|river|lake|coast|bay)/i;
+  const darkVariant = darkenHex(color, 0.8);
   for (const layer of style.layers) {
-    if (layer.type !== 'fill') continue;
     const id = layer.id;
+    if (id.startsWith('bathymetry-')) continue;
+    if (id.startsWith('subcables-')) continue;
     const sourceLayer = String((layer as Record<string, unknown>)['source-layer'] ?? '');
-    if (!landRegex.test(id) && !landRegex.test(sourceLayer)) continue;
+    const isWater = waterRegex.test(id) || waterRegex.test(sourceLayer);
+    if (isWater) continue;
     try {
-      map.setPaintProperty(id, 'fill-color', color);
+      if (layer.type === 'background') {
+        map.setPaintProperty(id, 'background-color', color);
+      } else if (layer.type === 'fill') {
+        map.setPaintProperty(id, 'fill-color', darkVariant);
+      }
     } catch {
       // ignore
     }