He has been writing a weekly diary for the BBC News website and BBCMundo.com, describing the challenges and dangers he faced as he swam the nearly 5,400km (3,375 miles) from Peru to Brazil.
How did he cope with the piranhas?
“There are thousands of them. Often you find them closer to the shore. Three days ago we anchored our boat and threw meat into the river and immediately they started grabbing the meat. So if you are bleeding or you have an open wound they will catch you right away.
“So I never swim close to the banks. I stay in the middle and I put some gasoline and cream on my wetsuit to stop the piranhas from smelling my body. My team also can throw blood or meat on the other side of the boat to distract them.”