Kammala jumla mai zuwa: A Wasannin Olympics na 2004 a Athens, Lagoun ya cancanci zama dan wasa na mutum don maza 100 m butterfly. Ya share lokacin shigarwa na FINA B na 53.66 daga
Gasar Zakarun Turai a Madrid, Spain. Ya kalubalanci wasu masu iyo bakwai a zagayen na biyar, gami da babban zakara Milorad Čavić na Serbia da Montenegro. Ya yi tsere zuwa matsayi na biyar ta hanyar 0.24 na biyu a bayan Frédérick Bousquet na Faransa a 53.87. Lagoun ya kasa ci gaba zuwa wasan kusa da na karshe, yayin da ya sanya na ashirin da shida a cikin wasan farko.