Nick Vujicic, right, is accompanied by a life guard as he treads water in an acrylic enclosure keeping safe while diving among sharks, Thursday, Sept. 5, 2013 in Singapore. Vujicic, a Serbian Australian evangelist and motivational speaker born with tetra-amelia syndrome, a rare disorder characterized by the absence of all four limbs, is in the city-state to give a motivational talk and was visiting 'The Shark Encounter at Marine Life Park' at one of Singapore's main tourist attractions in Resorts World Sentosa