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).