Her last two major international competitions were the 2011 FINA World Championships in Shanghai, China and the Great Scottish Swim in Scotland. She was articulate with the media and a highly competitive athlete who reached the pinnacle of her chosen aquatic disciplines. She was a judge at the 2012 H2Open Awards organized by H2Open Magazine, an award designed to celebrate achievement in open water swimming.
Patten attended Plymouth College as a swimming scholar from the age of 11 to 18 where she was the house captain of Chaytor's House. Cassie was coached in the highly successful Plymouth Leander Swimming  programme at this time.
At the British Championships in 2006 she won a bronze in the 400 m and a silver in the 800 m. At the British Championships in 2007 she won a bronze in the 400 m freestyle and a silver in the 200 m butterfly. In her third year at the championships she won silver in the 800 m freestyle.
She won a silver medal in the 10 km freestyle at the 2007 World championship at only three seconds behind Larisa Ilchenko, the gold medalist. Patten represented Great Britain at the 2008 Summer Olympics in the 800 m freestyle and also in the Olympic 10K Marathon Swim where she won a bronze medal.
2011 FINA World Championships
Cassandra placed 21st (2:02:33.6) in the 2011 FINA World Championships in the 10K in Shanghai, China.