Add water and sky textures to underwater Gazebo world (#299)

* Consolidated worlds into a single file

* Added water and sky textures to underwater world

* what

* Remove random change

blue_description/gazebo/worlds/underwater.world

@@ -42,5 +42,26 @@
       <pose>0 7 -10 0 0 0</pose>
     </include>
 
+    <include>
+      <uri>
+        https://fuel.gazebosim.org/1.0/OpenRobotics/models/Coast Water
+      </uri>
+      <pose>0 0 0 0 0 0</pose>
+    </include>
+
+    <scene>
+      <ambient>1.0 1.0 1.0</ambient>
+      <background>0.8 0.8 0.8</background>
+      <sky></sky>
+    </scene>
+
+    <light type="directional" name="sun1">
+      <pose>50 0 150 0 0 0</pose>
+      <diffuse>1 1 1 1</diffuse>
+      <specular>.1 .1 .1 1</specular>
+      <direction>0.3 0.3 -1</direction>
+      <cast_shadows>false</cast_shadows>
+    </light>
+
   </world>
 </sdf>