Why sharks swim around you before they attack

[Brinjal]

Two great whites were swimming in the ocean when they saw a sinking boat.
Folow me son says the father shark and they swam to the boat.
First we swin around them a couple of times with just the tip of our fins showing. And they did.
Well done son now we swim around them with the whole of our fin showing out of the water. and they did.
Now we eat them. And they did.
When they were gorged the son asked his father Dad why didnt we just eat them instead of all that swimming around?
Wise father replied. Because they taste better with all the sh.te out of them.