  In February 2006, Swift caught a GRB in the act of turning into a supernova,
and made the first ever direct observations of the break-out and early
expansion of a supernova shock wave. GRB 060218 began with an exceptionally
long burst of non-thermal gamma-rays, lasting over 2000 s, as a jet erupted
through the surface of the star. While this was in progress, an optically-thick
thermal component from the shock wave of the supernova explosion grew to
prominence, and we were able to track the mildly relativistic expansion of this
shell as the blackbody peak moved from the X-rays into the UV and optical
bands. The initial radius of the shock implied that it was a blue supergiant
which had exploded, but the lack of Hydrogen emission lines in the supernova
spectrum indicated a more compact star. The most likely scenario is that the
shock ploughed into the massive stellar wind of a Wolf-Rayet progenitor, with
the shock breaking out and becoming visible to us once it reached the radius
where the wind became optically-thin. I present the Swift observations of this
landmark event, and discuss the new questions and answers it leaves us with.
