Superluminous Supernovae (SLSN) are a class of astrophysical transients with a luminosity often 50 times greater than that of classical SNe. With only ~20 well studied objects of this class, their physical origin is still a mystery, with the birth and spin-down of a magnetar often cited as the most likely scenario. New observations show that some of these events are preceded by a blue and fast 'bump' in the light curve, which could be interpreted as a signature of shock-cooling of an extended stellar envelope.

The Dark Energy Survey (DES) supernova program is a large, multi-year imaging survey at the CTIO 4-m telescope designed to study high redshift supernovae. From the first three years of data, we have identified 13 spectroscopically confirmed superluminous supernovae and around 20 photometrically-selected candidate events out to redshift of 2, all with high-quality homogeneous multi-colour data. We will present an analysis of the early-time photometric data of this sample, constraining the presence and physical origin of initial 'bumps' in the light curves.