Die half body

A man lives in the city, and he goes to countryside to see natural view. To reach direction, he need to use boat. On the boat, he talks with with boatman.
Man: Do you know how to use smartphone?
Boatman: No, I cannot use it.
Man: It seems to die half body if you cannot use smartphone today.
Boatman: Do you how to swim?
Man: No, I don't
Boatman: If you do not know how to swim you will die full body because there is a storm coming.
Man: Gaga