The rate of change in the whale's depth is the change in depth divided by the time it takes for the change to occur. In this case, the change in depth is from 15 meters below the surface to the surface, which is a change of 15 meters. The time it takes for the change to occur is 9.5 seconds. Therefore, the rate of change in the whale's depth is: 15 meters / 9.5 seconds = 1.5789... meters/second. To the nearest hundredth, the rate of change in the whale's depth is 1.58 meters/second.
In other words, the whale is rising at a rate of 1.58 meters per second. So, every second, it rises 1.58 meters closer to the surface.