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 comments on Matthew 4:18].