The incident involving Jesus walking on water is the fifth of the seven signs recorded in detail by John in John 2–12. It is set in the evening after the feeding of the 5,000 recorded in John 6:1–15. Like the fourth sign, its timing is significant. Jesus’ encounter with the Jews in Jerusalem recorded in John 5 had raised the following questions: Is Jesus the prophet like Moses (something implied in the argument of John 5:45–47); and is he equal with God (John 5:18)? It is very significant, therefore, that Jesus is shown to have the power to walk on water, since walking on water is considered in the Old Testament to be uniquely an activity of God. By walking on water, Jesus thus showed himself to be divine and also greater than Moses. Moses after all had to wait until God made dry land appear before he could lead Israel across the sea at the time of the exodus, whereas Jesus had no such need. Jesus’ divinity can not only be seen in the fact of his walking on water, but also via his I am statement, and through the detail of the immediate arrival of the boat at its destination.
Summarizing the immediate events leading up to Jesus’walking on water, Jesus’ disciples had gotten into a boat to travel from the south-eastern area of the Sea of Galilee to Capernaum, a journey of some 10–15 km (John 6:17). A strong wind had been blowing, and when the disciples had reached to about halfway across the lake, they observed Jesus walking on the sea and approaching the boat (John 6:18–19). Jesus walking on the water is a theologically significant activity. It is a clear sign of Jesus’ deity. According to Old Testament teaching, only God has power over the sea (e.g., Gen 1:6–7, 9; Exod 14:21; 15:8; Job 26:12; 41:31; Ps 33:7; 74:13; 95:5; 104:6–7; 107:25, 29; Isa 51:15). God is exalted above the sea (Ps 93:3–4; 104:3). Job 9:8 teaches that God “treads upon the waves of the sea” (see also Isa 43:16; Ps 77:19). The sea is also a symbol of the forces of chaos (Gen 1:2; Ps 88:9–10; Isa 51:9–10; Dan 7:2–3; Rev 13:1; 21:1). Sinking into water is also an Old Testament metaphor for death (Ps 69:14–15). By walking on water, Jesus proved that he is divine, and that he has power over the forces of chaos and death. This sign, therefore, gives clear evidence to prove that Jesus is indeed the Son of God, with power and authority equal with the Father (contra the attitude of the Jews in 5:18).
Jesus walking on the water and approaching the boat initially only provoked fear in the disciples; but responding to this fear, Jesus said, “It is I. Do not be afraid” (John 6:20). Both clauses in Jesus’ response are significant. The clause translated as it is I literally reads as I am (ἐγώ εἰμι) in the original Greek. The expression ἐγώ εἰμι often functions in Greek as the equivalent of the English it is I or it is me. Nevertheless, in a context which stresses Jesus’ deity, we are most likely meant to understand Jesus’ I am statement as echoing the divine name Yahweh, which is linked in Exod 3:14 with the Hebrew verb אהיה I am. The implication is, therefore, that Jesus is Yahweh in the flesh (see also Isa 41:4; 43:10). Jesus’ I am statements occur elsewhere in John’s Gospel (see John 4:26; 8:24, 28, 58; 13:19; 18:5–6, 8). There are also many I am X statements made by Jesus in John’s Gospel (e.g., 6:35, 51; 8:12; 10:7, 11). Jesus’ command do not be afraid also echoes similar statements made by God elsewhere in the Bible (e.g., Gen 26:24; Exod 14:13; Deut 31:6, 8; and especially Isa 43:1–2, 5). Because none other than Yahweh was with them, they need not have been afraid.
Jesus boarded the boat presumably shortly after his disciples had rowed “about twenty-five or thirty stadia” (John 6:19). One stadium is about 185 m in length. This means that the disciples had rowed about 5 km, which indicates that their location at that point was about halfway across the lake. Yet in John 6:21 we read that when Jesus got into the boat, “immediately the boat was at the land to which they were going.” Jesus delivered his disciples safely and almost instantaneously through the stormy sea to their destination. This detail is theologically significant, because guiding people through a stormy sea safely to the shore is a divine act according to the Old Testament (see Ps 107:23–30; see also Jonah 1:11–17; 2:10).
All in all, the sign of Jesus’ walking on water functions in John’s Gospel to prove Jesus’ divinity.