Why sharks circle round you before attacking,

 Two great white sharks swimming in the ocean spied survivors of a
> sunken ship. "Follow me son" the father shark said to the son shark
> and they swam to the mass of people. "First we swim around them a few
> times with just the tip of our fins showing." And they did. "Well
> done, son! Now we swim around them a few times with all of our fins
> showing." And they did. "Now we eat everybody." And they did.
> When they were both gorged, the son asked, "Dad, why didn't we just
> eat them all at first? Why did we swim around and around them?"
> His wise father replied, "Because they taste better without the shit 
> inside!"