mark 6:48 And he saw them 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. - Free Bible Online

      48. And he saw them toiling in rowing; for the wind was contrary unto them--putting forth all their strength to buffet the waves and bear on against a head wind, but to little effect. He "saw" this from His mountain top, and through the darkness of the night, for His heart was all with them: yet would He not go to their relief till His own time came.
      and about the fourth watch of the night--The Jews, who used to divide the night into three watches, latterly adopted the Roman division into four watches, as here. So that, at the rate of three hours to each, the fourth watch, reckoning from six P.M., would be three o'clock in the morning. "So when they had rowed about five and twenty or thirty furlongs" (Joh 6:19) --rather more than halfway across. The lake is about seven miles broad at its widest part. So that in eight or nine hours they had only made some three and a half miles. By this time, therefore, they must have been in a state of exhaustion and despondency bordering on despair; and now at length, having tried them long enough.
      he cometh unto them, walking upon the sea--"and draweth nigh unto the ship" (Joh 6:19).
      and would have passed by them--but only in the sense of Lu 24:28; Ge 32:26; compare Ge 18:3, 5; 42:7.

JFB.