And Peter answered Him and said, “Lord, if it is You, command me to come to You on the water.” So Jesus said, “Come.” And when Peter had come down out of the boat, he walked on the water to go to Jesus (Matthew 14:22-23).

Peter walked on water, not because he was strong in willpower, but because He was trusting in God's power. You see, it was Jesus that commanded Peter to "come" out of the boats security, and it was Jesus who granted him the power to walk on impossibilities. When Jesus speaks, power follows.