John presents the narrative without Christ commenting on the disciples' decision to fish. Though His promises to go before them to Galilee are clear, in the opening verses of John 21, we find seven of the disciples following Peter to go fishing. No casual occasion for leisure, this fishing trip is a commitment to many hours of hard work.
Obviously, these are difficult days for the disciples. They had spent most of the past three-plus years in the direct company of Jesus. Even though He informed them several times of His impending death and resurrection (Mark 8:31; Matthew 16:21; 26:2), the disciples are still deeply troubled by the former and confounded by the latter (Luke 24:36-41; Matthew 28:17). Peter is particularly distraught, still shamefaced from having denied Him three times (Luke 22:61-62; John 21:17).
Even though they are filled with joy in the presence of the post-resurrection Christ, they also realize that times are changing. They recognize that their future is more uncertain—and probably more difficult—than they desire. We can easily understand their need to engage in an activity with which they are familiar and comfortable, and which removes them from prying eyes and ears.
Martin G. Collins
The Miracles of Jesus Christ: A Second Large Catch of Fish (Part One)