John 6:21 (NIV)
Then they were willing to take Him into the boat.
Some folks are only willing to accept Christ and His salvation if they receive some personal reassurance from God. In this case, the disciples were not impressed by the tremendous power the Lord demonstrated when He walked on water. Instead, they were terrified. Then follows the most simple reassurance from Christ, "don't be afraid." Only then were the disciples willing to take Him into the boat.
When God displayed His awesome power as He did on Mt. Sinai (Exodus 19:18-19), the Israelites were terrified (Exodus 20:18). Sometimes, God's awesomeness will frighten us into running away from Him. It's His gentleness that follows (1 Kings 19:12) that makes us willing to accept Him.