Explain how to determine the following from the graph:

Number of times the barnacle went beneath the water level if the boat traveled a distance of 20 m

Number of meters of the 20 m trip that the barnacle was underwater

It is going to be 40 m underwater

When the graph is below the x-axis, the barnacle is underwater. The graph dips below the x-axis three times between x = 0 and x = 20, so the barnacle goes underwater three times. Every time the barnacle goes underwater, the boat travels meters (one half the circumference of the wheel) before the barnacle comes back up, so the barnacle covers 3 meters underwater between x = 0 and x = 20.