St. Mark 6:47-51

" And when even was come, the ship was in the midst of the sea, and he alone on the land.
"And he [the Savior] saw them [the disciples] toiling in rowing; for the wind was contrary unto them: and about the fourth watch of the night he cometh unto them, walking upon the sea, and would have passed by them.
"But when they saw him walking upon the sea, they supposed it had been a spirit, and cried out:
"For they all saw him, and were troubled. And immediately he talked with them, and saith unto them, Be of good cheer: it is I; be not afraid."

"Into every adult human life come experiences like unto the battling of the storm tossed voyagers with contrary winds and threatening seas, ofttimes the night of struggle and danger is far advanced before succor appears; and then too frequently the saving aid is mistaken for a greater terror. As came unto Peter and his terrified companions in the midst of the turbulent waters so comes to all who toil in faith, the voice of the deliverer- 'It is I; be not afraid.'"
James E. Talmage, "Jesus the Christ" p. 313-314