Ace arrives by chartered plane in the Wumba Chumba Islands and visits biologist Dr. Tasman to test water contamination levels in the ocean and estuaries. Ace must study tides and complete Dr. Tasman's tide graph (Activity 6), to interpret the salinity levels of fresh and salt water, with the presence of toxins. Upon discovering that toxin levels are higher in the ocean water (Activity 7), Ace concludes the contaminants are coming from the sea and not from the estuary. After Dr. Tasman sends her research team out to test mussels for contamination along the shoreline, Ace helps to plot the results of the tests on a map of the Wumba Chumba Islands as the hunt for the exact location of the barrels is narrowed down (Activity 8).