From Morton's link
What the propagandists wanted was a trail of bombs released in sequence, the first bomb exploding on impact with the sea before the last bomb left the aeroplane, the intention being to create a ‘wall of water’ as an impressive spectacle.
and my calculations you can see that the vertical stack of bombs would have been about 1,800 feet with standard spacing and assuming a low level drop to achieve the aim the aircraft would have been in the 1% range of frag damage from ONE bomb and well inside the blast range damage zone.
PS, they never let us Vulcans drop HE out there after the odd Victor 'heard but not seen' on both China Rock and S2.