What is the fastest marine mammal?

The 2012 Summer Olympics are less than 10 days away and with this comes lots of intense swimming competitions (among other events). This got me wondering, if I lined up various species of marine mammals which one would be taking home the gold? Check out the average top speeds of 10 species in the graph below. (Now time to get the image of an orca wearing a Speedo out of my mind.)


1. http://www.speedofanimals.com/water
2. http://en.wikipedia.org/wiki/Porpoise
3. http://marinebio.org/oceans/marine-mammals.asp