sheared long water pump bolt

while i was taking off of my water pump i sheared one of the long bolts. has anyone got advice about putting the new pump back without replacing the bust bolt.
will it leak?
should i strip off back to the engine block where it seems to be threaded from?
how do i get at the broken off bolt ?
does anyone have any advice for me please ? (help!)

its not a long job to remove housing ,then to get at bolt if its not sheared flush with block hit end of stud a few times hard ,shock helps free it ,if flush it will need to be drilled akterrnator will lay to one side and so will pas pump if you remove 4 bolts that hold bracket to housing

thanks james
i got it off.after a struggle
will use lots of gasket compound where the damage was done
thanks for the advice