Paul Taylor, 50, of West Norwood, said the disaster was the worst seen by his response charity Team Rubicon UK.
He told of a 14-year-old who nearly “gave up” while clinging to a rope with his family for two days in freezing water but was “amazingly resilient” — and a man who “floated on a fridge for 14 hours”.
At least 50 died, 1,300 were missing and 76,000 homeless after the category-five hurricane last month.
Mr Taylor said: “Streets had turned into rivers. There was a stench of death.”
Team Rubicon UK worked on some of the worst-hit islands.