Waterfall charts are not standard in the Office library, but they are often used and can be created fairly easy.
This tutorial demonstrates how to create a waterfall chart, completely done in Powerpoint.
Step 1. Insert a Stacked bar chart
Step 2. Edit the excel data
Right click on the chart and select Edit data. Enter the following series and values:
Your chart should look something like this:
Step 3. Change the chart series