diff --git a/src/client/graphics/layers/UnitLayer.ts b/src/client/graphics/layers/UnitLayer.ts
index 3dd62c8e2..5f3227226 100644
--- a/src/client/graphics/layers/UnitLayer.ts
+++ b/src/client/graphics/layers/UnitLayer.ts
@@ -137,7 +137,7 @@ export class UnitLayer implements Layer {
 
       clickRef = this.game.ref(cell.x, cell.y);
     }
-    if (!this.game.isOcean(clickRef)) return;
+    if (!this.game.isWater(clickRef)) return;
 
     if (this.selectedUnit) {
       this.eventBus.emit(
@@ -169,13 +169,13 @@ export class UnitLayer implements Layer {
     const clickRef = this.game.ref(cell.x, cell.y);
     if (this.game.inSpawnPhase()) {
       // No Radial Menu during spawn phase, only spawn point selection
-      if (!this.game.isOcean(clickRef)) {
+      if (!this.game.isWater(clickRef)) {
         this.eventBus.emit(new MouseUpEvent(event.x, event.y));
       }
       return;
     }
 
-    if (!this.game.isOcean(clickRef)) {
+    if (!this.game.isWater(clickRef)) {
       // No warship to find because no Ocean tile, open Radial Menu
       this.eventBus.emit(new ContextMenuEvent(event.x, event.y));
       return;
diff --git a/src/core/execution/PortExecution.ts b/src/core/execution/PortExecution.ts
index 9483f1b70..3dc05724e 100644
--- a/src/core/execution/PortExecution.ts
+++ b/src/core/execution/PortExecution.ts
@@ -97,10 +97,22 @@ export class PortExecution implements Execution {
   // It's a probability list, so if an element appears twice it's because it's
   // twice more likely to be picked later.
   tradingPorts(): Unit[] {
+    const sourceComponents = new Set<number>();
+    for (const neighbor of this.mg.neighbors(this.port!.tile())) {
+      if (!this.mg.isWater(neighbor)) continue;
+      const comp = this.mg.getWaterComponent(neighbor);
+      if (comp !== null) sourceComponents.add(comp);
+    }
     const ports = this.mg
       .players()
       .filter((p) => p !== this.port!.owner() && p.canTrade(this.port!.owner()))
       .flatMap((p) => p.units(UnitType.Port))
+      .filter((p) => {
+        for (const comp of sourceComponents) {
+          if (this.mg.hasWaterComponent(p.tile(), comp)) return true;
+        }
+        return false;
+      })
       .sort((p1, p2) => {
         return (
           this.mg.manhattanDist(this.port!.tile(), p1.tile()) -
diff --git a/src/core/execution/TradeShipExecution.ts b/src/core/execution/TradeShipExecution.ts
index 9eaa2c092..0f3df5f7b 100644
--- a/src/core/execution/TradeShipExecution.ts
+++ b/src/core/execution/TradeShipExecution.ts
@@ -90,13 +90,16 @@ export class TradeShipExecution implements Execution {
       this.wasCaptured &&
       (tradeShipOwner !== dstPortOwner || !this._dstPort.isActive())
     ) {
+      const myComponent = this.mg.getWaterComponent(curTile);
       const nearestPort = findClosestBy(
         tradeShipOwner.units(UnitType.Port),
         (port) => this.mg.manhattanDist(port.tile(), curTile),
         (port) =>
           port.isActive() &&
           !port.isMarkedForDeletion() &&
-          !port.isUnderConstruction(),
+          !port.isUnderConstruction() &&
+          myComponent !== null &&
+          this.mg.hasWaterComponent(port.tile(), myComponent),
       );
       if (nearestPort === null) {
         this.tradeShip.delete(false);
diff --git a/src/core/execution/WarshipExecution.ts b/src/core/execution/WarshipExecution.ts
index e8b736bc2..527056df6 100644
--- a/src/core/execution/WarshipExecution.ts
+++ b/src/core/execution/WarshipExecution.ts
@@ -254,7 +254,7 @@ export class WarshipExecution implements Execution {
       }
       const tile = this.mg.ref(x, y);
       if (
-        !this.mg.isOcean(tile) ||
+        !this.mg.isWater(tile) ||
         (!allowShoreline && this.mg.isShoreline(tile))
       ) {
         attempts++;
diff --git a/src/core/execution/nation/NationStructureBehavior.ts b/src/core/execution/nation/NationStructureBehavior.ts
index fe9698abd..43ec27a8a 100644
--- a/src/core/execution/nation/NationStructureBehavior.ts
+++ b/src/core/execution/nation/NationStructureBehavior.ts
@@ -90,6 +90,7 @@ export class NationStructureBehavior {
     cluster: Cluster | null;
     weight: number;
   }> | null = null;
+  private _sharedWaterComponents: Set<number> | null = null;
 
   constructor(
     private random: PseudoRandom,
@@ -107,7 +108,8 @@ export class NationStructureBehavior {
           Math.floor(this.player.numTilesOwned() / TILES_PER_CITY_EQUIVALENT),
         )
       : this.player.unitsOwned(UnitType.City);
-    const hasCoastalTiles = this.hasCoastalTiles();
+    this._sharedWaterComponents = this.sharedWaterComponents();
+    const hasCoastalTiles = this._sharedWaterComponents !== null;
 
     // Build order for non-city structures (priority order)
     const buildOrder: UnitType[] = [
@@ -165,11 +167,37 @@ export class NationStructureBehavior {
     return false;
   }
 
-  private hasCoastalTiles(): boolean {
+  /**
+   * Returns the set of water components shared with at least one other player,
+   * or null if there are none.
+   */
+  private sharedWaterComponents(): Set<number> | null {
+    // Collect all water-component IDs reachable from this player's coast.
+    const playerComponents = new Set<number>();
     for (const tile of this.player.borderTiles()) {
-      if (this.game.isOceanShore(tile)) return true;
+      if (!this.game.isShore(tile)) continue;
+      for (const neighbor of this.game.neighbors(tile)) {
+        if (!this.game.isWater(neighbor)) continue;
+        const comp = this.game.getWaterComponent(neighbor);
+        if (comp !== null) playerComponents.add(comp);
+      }
     }
-    return false;
+    if (playerComponents.size === 0) return null;
+
+    // Keep only components that at least one other player also touches.
+    const shared = new Set<number>();
+    for (const other of this.game.players()) {
+      if (other === this.player) continue;
+      for (const tile of other.borderTiles()) {
+        if (!this.game.isShore(tile)) continue;
+        for (const neighbor of this.game.neighbors(tile)) {
+          if (!this.game.isWater(neighbor)) continue;
+          const comp = this.game.getWaterComponent(neighbor);
+          if (comp !== null && playerComponents.has(comp)) shared.add(comp);
+        }
+      }
+    }
+    return shared.size > 0 ? shared : null;
   }
 
   /**
@@ -471,10 +499,19 @@ export class NationStructureBehavior {
     return bestTile;
   }
 
+  /** Samples shore tiles adjacent to water reachable by another player (=> trading possible) */
   private randCoastalTileArray(numTiles: number): TileRef[] {
-    const tiles = Array.from(this.player.borderTiles()).filter((t) =>
-      this.game.isOceanShore(t),
-    );
+    const shared = this._sharedWaterComponents;
+    const tiles = Array.from(this.player.borderTiles()).filter((t) => {
+      if (!this.game.isShore(t)) return false;
+      if (shared === null) return false;
+      for (const neighbor of this.game.neighbors(t)) {
+        if (!this.game.isWater(neighbor)) continue;
+        const comp = this.game.getWaterComponent(neighbor);
+        if (comp !== null && shared.has(comp)) return true;
+      }
+      return false;
+    });
     return Array.from(this.arraySampler(tiles, numTiles));
   }
 
diff --git a/src/core/execution/nation/NationWarshipBehavior.ts b/src/core/execution/nation/NationWarshipBehavior.ts
index df240f03f..51b469954 100644
--- a/src/core/execution/nation/NationWarshipBehavior.ts
+++ b/src/core/execution/nation/NationWarshipBehavior.ts
@@ -74,7 +74,7 @@ export class NationWarshipBehavior {
       }
       const tile = this.game.ref(randX, randY);
       // Sanity check
-      if (!this.game.isOcean(tile)) {
+      if (!this.game.isWater(tile)) {
         continue;
       }
       return tile;
diff --git a/src/core/execution/utils/AiAttackBehavior.ts b/src/core/execution/utils/AiAttackBehavior.ts
index c42301cc7..738fe6893 100644
--- a/src/core/execution/utils/AiAttackBehavior.ts
+++ b/src/core/execution/utils/AiAttackBehavior.ts
@@ -109,15 +109,15 @@ export class AiAttackBehavior {
       return;
     }
 
-    // Check if we have any ocean shore tiles to launch from
-    const oceanShore = Array.from(this.player.borderTiles()).filter((t) =>
-      this.game.isOceanShore(t),
+    // Check if we have any shore tiles to launch from
+    const shore = Array.from(this.player.borderTiles()).filter((t) =>
+      this.game.isShore(t),
     );
-    if (oceanShore.length === 0) {
+    if (shore.length === 0) {
       return;
     }
 
-    const src = this.random.randElement(oceanShore);
+    const src = this.random.randElement(shore);
 
     // First look for high-interest targets (unowned or bot-owned). Mainly relevant for earlygame
     let dst = this.findRandomBoatTarget(src, borderingEnemies, true);
@@ -574,11 +574,11 @@ export class AiAttackBehavior {
       return null;
     }
 
-    // Check if we have any ocean shore tiles to launch from
-    const hasOceanShore = Array.from(this.player.borderTiles()).some((t) =>
-      this.game.isOceanShore(t),
+    // Check if we have any shore tiles to launch from
+    const hasShore = Array.from(this.player.borderTiles()).some((t) =>
+      this.game.isShore(t),
     );
-    if (!hasOceanShore) return null;
+    if (!hasShore) return null;
 
     const filteredPlayers = this.game.players().filter((p) => {
       if (p === this.player) return false;
@@ -615,10 +615,10 @@ export class AiAttackBehavior {
       const closest = closestTwoTiles(
         this.game,
         Array.from(this.player.borderTiles()).filter((t) =>
-          this.game.isOceanShore(t),
+          this.game.isShore(t),
         ),
         Array.from(entry.player.borderTiles()).filter((t) =>
-          this.game.isOceanShore(t),
+          this.game.isShore(t),
         ),
       );
       if (closest === null) continue;
@@ -786,10 +786,8 @@ export class AiAttackBehavior {
   private sendBoatAttack(target: Player) {
     const closest = closestTwoTiles(
       this.game,
-      Array.from(this.player.borderTiles()).filter((t) =>
-        this.game.isOceanShore(t),
-      ),
-      Array.from(target.borderTiles()).filter((t) => this.game.isOceanShore(t)),
+      Array.from(this.player.borderTiles()).filter((t) => this.game.isShore(t)),
+      Array.from(target.borderTiles()).filter((t) => this.game.isShore(t)),
     );
     if (closest === null) {
       return;
diff --git a/src/core/game/PlayerImpl.ts b/src/core/game/PlayerImpl.ts
index b223b2f62..05a90d1a6 100644
--- a/src/core/game/PlayerImpl.ts
+++ b/src/core/game/PlayerImpl.ts
@@ -1222,7 +1222,7 @@ export class PlayerImpl implements Player {
         manhattanDistFN(tile, this.mg.config().radiusPortSpawn()),
       ),
     )
-      .filter((t) => this.mg.owner(t) === this && this.mg.isOceanShore(t))
+      .filter((t) => this.mg.owner(t) === this && this.mg.isShore(t))
       .sort(
         (a, b) =>
           this.mg.manhattanDist(a, tile) - this.mg.manhattanDist(b, tile),
@@ -1239,14 +1239,19 @@ export class PlayerImpl implements Player {
   }
 
   warshipSpawn(tile: TileRef): TileRef | false {
-    if (!this.mg.isOcean(tile)) {
+    if (!this.mg.isWater(tile)) {
       return false;
     }
 
+    const tileComponent = this.mg.getWaterComponent(tile);
     const bestPort = findClosestBy(
       this.units(UnitType.Port),
       (port) => this.mg.manhattanDist(port.tile(), tile),
-      (port) => port.isActive() && !port.isUnderConstruction(),
+      (port) =>
+        port.isActive() &&
+        !port.isUnderConstruction() &&
+        tileComponent !== null &&
+        this.mg.hasWaterComponent(port.tile(), tileComponent),
     );
 
     return bestPort?.tile() ?? false;
diff --git a/src/core/game/WaterManager.ts b/src/core/game/WaterManager.ts
index d3960b010..69009d5be 100644
--- a/src/core/game/WaterManager.ts
+++ b/src/core/game/WaterManager.ts
@@ -216,14 +216,6 @@ export class WaterManager {
         }
       }
     }
-    // If no converted tile is adjacent to existing ocean (e.g. all-land map),
-    // mark all converted tiles as ocean so they're navigable for ports/boats.
-    if (oceanQueue.length === 0) {
-      for (const tile of converted) {
-        map.setOcean(tile);
-        oceanQueue.push(tile);
-      }
-    }
     let oHead = 0;
     while (oHead < oceanQueue.length) {
       const tile = oceanQueue[oHead++];
diff --git a/tests/nukes/WaterNukes.test.ts b/tests/nukes/WaterNukes.test.ts
index 2607c4e14..91a65e739 100644
--- a/tests/nukes/WaterNukes.test.ts
+++ b/tests/nukes/WaterNukes.test.ts
@@ -180,42 +180,6 @@ describe("Water Nukes", () => {
     });
   });
 
-  describe("all-land map (no pre-existing ocean)", () => {
-    test("nuke-created water gets ocean bit so ports can be built", async () => {
-      game = await setup("plains", {
-        infiniteGold: true,
-        instantBuild: true,
-        waterNukes: true,
-      });
-      const info = new PlayerInfo("p", PlayerType.Human, null, "p");
-      game.addPlayer(info);
-      game.addExecution(new SpawnExecution(gameID, info, game.ref(1, 1)));
-      while (game.inSpawnPhase()) game.executeNextTick();
-      player = game.player(info.id);
-      constructionExecution(game, player, 1, 1, UnitType.MissileSilo);
-
-      const target = game.ref(10, 10);
-
-      // Verify no ocean exists anywhere near the target before the nuke
-      expect(game.isLand(target)).toBe(true);
-
-      launchNukeAt(game, player, target);
-      tickUntilNukeLands(game);
-
-      // The converted tile should be ocean (not just lake water)
-      expect(game.isWater(target)).toBe(true);
-      expect(game.isOcean(target)).toBe(true);
-
-      // Neighboring land tiles should be ocean-shore (required for port placement)
-      const x = game.x(target);
-      const y = game.y(target);
-      const shoreCandidate = game.ref(x + 2, y);
-      if (game.isLand(shoreCandidate)) {
-        expect(game.isOceanShore(shoreCandidate)).toBe(true);
-      }
-    });
-  });
-
   describe("updateTile terrain byte round-trip", () => {
     test("terrain byte is packed and unpacked correctly", async () => {
       game = await setup("plains", {