Stravius appeared on the world stage at the 2009 European Short Course Swimming Championships in Istanbul where he was part of the winning 4 × 50 m freestyle relay and finished in the top 8 in the 50 m breaststroke. The next year at the 2010 European Short Course Swimming Championships in Hungary, Stravius won his first medal at an international meet, winning a silver in the 100 m backstroke. At this meet, he also was part of the winning 4 × 100 m medley relay and the bronze medal winning team of the 4 × 200 m freestyle relay. Stravius won his first international gold winning the gold medal in the 100 m backstroke at the 2011 FINA World Championships in Shanghai. He shared it with countryman Camille Lacourt. He also received a silver in the 4 × 100 m freestyle relay and the 4 × 200 m freestyle relay at this meet.