If you read John 6, there’s a passage that doesn’t seem to belong, right? John 6:16-21 is a passage that feels out of place until you consider what it indicates. Take this as part 2 of the chapter.
Part 1 is Jesus multiplying the bread and fishes. That shows that as God, he can do something seemingly impossible and multiply. This sets up that Jesus can indeed feed us his body and blood because he has that power.
Part 2 is the scene on the boat I mentioned. What happened here is that Jesus appears to his disciples while walking on the water. The Apostles say that this is a ghost, but Jesus says it is really him and they believe and take him in the boat. Now we know from the equivalent in Matthew 14 that this scene has Peter walk on water as well to meet Jesus and then due his shaken faith, falls into the water. Now if the point of the rest of the chapter was solely to say “Believe in Jesus,” then wouldn’t it make more sense for John to expand? However, the point of this inclusion appears rather to be to set up for Jesus to show that even though it may be impossible for something to be him, it is him.
These two parts set up the Bread of Life discourse and set it up so that we can truly believe that he speaks about his body and blood as real food and drink and that our spiritual life depends upon it.