This Bible says that he who believes and is baptized will be saved; but he who does not believe will be condemned. The verse in Mark you referenced seems to refer only to the fact that you are condemned if you do not believe. Do what Walter Martin does and refer to the verse before 16:16. 16:15 refers to the Gospel, not getting wet.

As to where it says that Jesus was baptized for those who can't be. . . I 'm not so sure. Except for the verse in the Bible where it points out the thief on the Cross got to go to Heaven despite not really being in any position to be baptized.