Mark 1:16

Now as he walked by the sea of Galilee ,.... The same with the sea of Tiberias, John 6:1 ,

he saw Simon : whose surname was Peter, the son of Jonas:

and Andrew his brother ; the brother of Simon,

casting a net into the sea ; of Galilee, in order to catch fish:

for they were fishers : by occupation, this was their trade and business, by which they got their livelihood; See Gill on Matthew 4:18 .