Mark, in his Gospel, says that Jesus from the mountainside saw the disciples straining at the oars. Although it was a stormy evening, we are not told that this storm frightened the disciples. Maybe they had been in many like it. Jesus came to them at the fourth watch, which was about 3am. They had left before 6pm on the previous day (that was when evening commenced), so they had been at sea for about nine hours, and had not rowed very far. Whatever else we can deduce about the time, we can say that Jesus chose when to come to their relief.
The Gospel writers all say that the disciples were making little progress because of the storm and they also describe Jesus as having no difficulty making progress as he crossed the sea. Indeed, Mark says that he was about to walk past the boat in which the disciples were. Surely the lesson from this is that what was difficult for the disciples was easy for Jesus. What held them back did not hold him back. The storm was a problem that they had, but it was not a problem that Jesus had. Instead of being a barrier to his progress, it was the road on which he moved ahead.
Another obvious lesson is that Jesus is Lord of creation. During the previous journey, he had commanded the storm to cease, and it did. On this journey, he does what would have been regarded as impossible when he walks on the waves. No doubt, the disciples would have deduced later that there is nothing in the creation that can hinder Jesus when he wants to do something.
The initial response of the disciples to this visible form walking on the waves was that they were seeing a ghost. Obviously they did not recognise that it was Jesus. They were terrified. We are not told that they prayed, yet their fear was recognised by Jesus and he spoke words of comfort to them. It is good to know that Jesus does not judge situations by our performance, because on this occasion the disciples got it all wrong.
What comfort did Jesus give to them? The answer is himself. He did not remove the storm immediately, which is what they might have wanted him to do. Instead he wanted them to know that he was in charge of circumstances, even those that were difficult to handle. They also needed to know more about him and his abilities.