Mark 6:50

For they all saw him, and were troubled
Had it been only seen by one, it might have been thought a fancy, and the effect of mere imagination; but as every one saw it, it was out of all doubt that so it was, and which gave them the greater concern:

and immediately he talked with them;
as soon as they saw him, "that very moment", as the Syriac renders it; that so by hearing his voice their fears might be allayed:

and saith unto them, be of good cheer, it is I, be not afraid;
(See Gill on Matthew 14:27).