John Gill

And when he had gone a little further thence,.... From the place where Simon and Andrew were casting their nets, though still by the sea side; he saw James the son of Zebedee, and John his brother. The former was be whom afterwards Herod killed with the sword, and the latter the beloved disciple; these were also fishermen: who also were in the ship mending their nets: as the other two disciples were on board the ship, casting their nets into the sea to catch fish; these were also in a ship, repairing their nets, in order to use them the same way, and for the same purpose; See Gill on Mat 4:21.