A paved path, exposed at low water, allows easy access but this is covered at high tide.
The man was wearing normal clothes and was not equipped for the icy waters, which were 7C and “extremely cold”, rescuers said.
The man had set off at 08:00.
Once on the lifeboat he was wrapped in warm blankets and it was “assessed that an ambulance and rapid evacuation would be required”.
The lifeboat went to Granton harbour where the rescued man was picked up by the Scottish Ambulance Service crew.
Stewart Atkinson, of RNLI Queensferry Lifeboat, told BBC Scotland News: “It was lucky that we got there when we did, as the casualty was extremely cold and was drifting further offshore, with the tide and offshore wind.
“This incident highlights that blow-up toys and airbeds are designed for pools, not the sea where they can quickly be blown offshore.
“Always check the forecast and tide conditions, be aware that conditions inshore may seem fine, but further offshore they can be significantly worse.
“Always wear a personal floatation device and make sure you are also wearing clothing suitable for the forecasted weather.”