In the section four introductory newscast, Ace learns that Captain Cecille Celebes of the HMS Bossanova has pledged the use of her entire ship and staff to the cause of pinpointing the pollutants off the Wumba Chumba Islands. Ace finally meets up with Paula Pacific, who recently arrived on the Islands, at the famous House of Waffles. Paula reports that she has not had any success following her leads and confirms that the key to solving this case is finding the barrels. Ace must now join the crew on the HMS Bossanova and assist in the search.
On-board Ace meets Toller, the crew member who tracks ocean currents by dropping buoys off at various points in the sea. A card is attached to each buoy so finders can return it with information about its final destination. This information helps Toller plot the route of the buoys and determine the direction of the ocean's currents. Buoys were dropped off yesterday and Toller informs Ace that he is expecting the cards back very soon.
While waiting, Ace visits Miho Mallaca in the sonar room. Miho is creating a map of the ocean floor and she describes various features of the seafloor as the boat passes over them. Ace then helps Miho to enter the depths from the profile and create a computer generated map of the ocean floor (Activity 9).
Back on deck, Toller now needs Ace's help to plot the final destinations of the buoys on a map of the Wumba Chumba Islands (Activity 10). The final map shows the directions the currents have been travelling, information necessary to locate the barrels in the sea.
Ace visits the bridge of the ship and meets Captain Cecille Celebes. Cecille tells Ace that by combining the shoreline data with the currents map, s/he can begin to guess where the barrels might be (Activity 11). Once Ace selects a spot to explore, the Bossanova heads to that area and Ace continues the search in a one-person submersible. If Ace is not successful in locating the barrels, s/he must return to the surface and pick another spot. This continues until Ace selects the correct location and discovers the barrels on the ocean floor below.
After successfully locating the barrels on the ocean floor, Ace's achievements are honoured at a special gathering of townspeople and scientists who helped in the investigation. Ace is thanked not only for finding the contaminated barrels but for reminding everyone about the importance of protecting the ocean.