Jamieson, Fausset and Brown on John 6:25

25. when they had found him on the other side--at Capernaum.

they said, &c.--astonished at His being there, and wondering how He could have accomplished it, whether by land or water, and when He came; for being quite unaware of His having walked upon the sea and landed with the disciples in the ship, they could not see how, unless He had travelled all night round the head of the lake alone, He could have reached Capernaum, and even then, how He could have arrived before themselves.