diff --git a/frontend/src/hooks/useKoreaData.ts b/frontend/src/hooks/useKoreaData.ts
index cec7547..71272b0 100644
--- a/frontend/src/hooks/useKoreaData.ts
+++ b/frontend/src/hooks/useKoreaData.ts
@@ -145,24 +145,27 @@ export function useKoreaData({
   // Propagate Korea aircraft (live only — no waypoint propagation needed)
   const aircraft = useMemo(() => propagateAircraft(baseAircraftKorea, currentTime), [baseAircraftKorea, currentTime]);
 
-  // Pre-compute mtCategory/natGroup on base data change (5-min polling)
-  // useState 값 직접 변경 불가 → 새 배열을 ref에 저장
-  const enrichedShipsRef = useRef<Ship[]>([]);
-  useMemo(() => {
-    enrichedShipsRef.current = baseShipsKorea.map(s => ({
+  // LIVE: baseShipsKorea 변경(5분 polling) 시에만 재계산. currentTime 무관.
+  // REPLAY: currentTime으로 활성 선박 + 웨이포인트 보간 필요.
+  const liveShips = useMemo(() =>
+    baseShipsKorea.map(s => ({
       ...s,
       mtCategory: getMarineTrafficCategory(s.typecode, s.category),
       natGroup: getNationalityGroup(s.flag),
-    }));
-  }, [baseShipsKorea]);
+    })),
+  [baseShipsKorea]);
 
-  // Korea region ships
-  // LIVE: enrichedShipsRef 동일 참조 반환 → 하위 useMemo 재실행 방지 (매초 currentTime 변경 무시)
-  // REPLAY: propagateShips로 위치 보간 → 새 배열 반환 (mtCategory는 spread로 상속)
-  const ships = useMemo(
-    () => isLive ? enrichedShipsRef.current : propagateShips(enrichedShipsRef.current, currentTime, false),
-    [baseShipsKorea, currentTime, isLive],
-  );
+  const replayShips = useMemo(() => {
+    if (isLive) return liveShips; // REPLAY 아니면 계산 안 함
+    const propagated = propagateShips(baseShipsKorea, currentTime, false);
+    for (const s of propagated) {
+      s.mtCategory = getMarineTrafficCategory(s.typecode, s.category);
+      s.natGroup = getNationalityGroup(s.flag);
+    }
+    return propagated;
+  }, [isLive, baseShipsKorea, currentTime, liveShips]);
+
+  const ships = isLive ? liveShips : replayShips;
 
   // Category-filtered data for map rendering (Set.has = O(1) per ship)
   const visibleAircraft = useMemo(