The Ferry Man

Johnson is a ferryman and he is caryying a Professor on his boat across the river.
What is the square root of 9? asked the Professor to Johnson.
I dont know, answered Johnson.
How do you spell elephant? the Prof asked again.
Johnson said, I have no idea.
Didnt you studied anything in school? Demaned the Prof in suprise.
No, said johnson.
Then you have wasted almost your life, the Professor said.
Johnson was silent for sometime and then said,
Can you swim?
The prof said, no.
Then you have wasted all your life, said Johnson. We are sinking.