I've noticed that many of the algae feeding mollusks (Astraea, Tegula, Turbo
etc) have a remarkable tendency to be quite aromatic when cleaned.  However,
when boiled quickly after capture as opposed to the "rotting" method, the
smells are not nearly as offensive.  Additionally, even the Strombus
(another algae eater) when allowed to rot are no walk in the park either.
 
Wayne Harland