mmm well the misfire and black plugs would definitely be related, so i would ignore other ignition issues for the moment.
are you certain it was water and not fuel?
if its water then theres no other way, other than a bhg.
its a bit strange that its in i all cylinders though, unless it has cracked beside each cylinder..?
how much water are we talking exactly?
do you mean enough to cover the piston top?