‘And when evening came, his disciples went down to the sea, and they boarded a boat and were going across the sea to Capernaum. And it was now dark and Jesus had not yet come to them.'
The other Gospels tell us that the boarding of the boat was at Jesus' command (Matthew 14:22), which it quite clearly was. The disciples would hardly have taken this course otherwise. The author is not so much a consummate storyteller as a theologian, and he misses out what he does not consider important. This incidentally helps to exonerate him from the charge of putting in details simply to give the effect of an eyewitness. He mentions them when he remembers them.
‘And it was now dark and Jesus had not yet come to them.' Perhaps John intends us to see that without Jesus the Apostles were still in darkness.