//smooth should now no longer pull water upwards.

src/HeightMap.java

@@ -123,7 +123,11 @@ public class HeightMap {
                 // Depending on growing or shrinking we need to start at the bottom or top
                 if (newHeight > curHeight) {
                     // Set the top block of the column to be the same type (this might go wrong with rounding)
-                    session.setBlock(new Vector(X, newHeight, Z), session.getBlock(new Vector(X, curHeight, Z)));
+                    BaseBlock existing = session.getBlock(new Vector(X, curHeight, Z));
+
+                    // Skip water/lava
+                    if (existing.getID() < 8 || existing.getID() > 11) {
+                        session.setBlock(new Vector(X, newHeight, Z), existing);
                         blocksChanged++;
 
                         // Grow -- start from 1 below top replacing airblocks
@@ -132,6 +136,7 @@ public class HeightMap {
                             session.setBlock(new Vector(X, originY + y, Z), session.getBlock(new Vector(X, originY + copyFrom, Z)));
                             blocksChanged++;
                         }
+                    }
                 } else if (curHeight > newHeight) {
                     // Shrink -- start from bottom
                     for (int y = 0; y < newHeight - originY; y++) {