In 2016, Burnell competed at the Rio Olympic Games, competing in the Marathon Swimming event, with the event beginning at the Copacabana Beach. In the Men's 10 Kilometre Open Water event at the 2016 Olympic Games, Burnell was disqualified for two yellow cards for unnecessary contact with other swimmers, after initially appearing to have finished fifth in a photo finish with the bronze medallist Marc-Antoine Olivier and Zu Lijun. The second yellow card came close to the finishing line after a tussle with the defending Olympic champion, Oussama Mellouli, who was also given a yellow card but ultimately finished 12th. In an angry interview following the race, Burnell claimed that Mellouli had grabbed his leg and that it may have stopped him from winning, and said the first card for unnecessary contact had been awarded when there were no other swimmers around. Burnell's appeal against the judges' decision was not successful.