On Fri, 29 Dec 2017 10:04:47 +0000 (GMT)
Tim+ wrote:

A bad idea for sure without removing the plugs but would a starter
motor have enough power to do more damage?

I imagine it would depend on the state of the engine when the starter
kicked in - if it picked up some momentum before locking then it might
bend a rod, but if the hydro-lock was pretty much instantaneous then I
doubt it. And if the water-full cylinder was on the exhaust stroke then
no harm done.