The TYR 'Darwin's Challenge' aquathlon is both an Adult & Junior event, which consists of an indoor swim in a flat form 25m pool. The juniors run is out and back laps on flat enclosed paths. Both the adults & youth categories run is an undulating course through the picturesque town of Shrewsbury and along the River Severn.

With a sting in the tail - 'Darwin's Challenge'! Age Categories and Distances as follows:
Adult Event: 17+yrs - 400m swim 5km run
Junior Event: TriStars Start: 8 years - 50m swim 600m run; TriStars 1: 9/10 yrs - 150m swim 1km run; TriStars 2: 11/12 yrs - 200m swim 2km run; TriStars 3: 13/14 yrs - 300m swim 3km run; Youth: 15/16 yrs - 400m swim 5km run.