The RNLI said he radioed the Coastguard when the barge headed the wrong way up the River Medway towards Sheerness.
The programme's producer said Spall was exhausted after a difficult 24 hours.
The RNLI said the crew of Sheerness lifeboat were receiving training in their boathouse when they overhead discussions between the barge and the Coastguard.
The lifeboat was launched at 21:30 BST after authorisation from the RNLI launch authority.
"There is lots of mud round there and you need to know where you are otherwise you can end up aground," said crew member Andy Matthews.
The barge was located about two miles from the lifeboat station at the entrance to Stangate Creek.
Crew member Nicki Wood boarded the barge and escorted it back to safety at Queenborough Harbour, where it mooored overnight.
Back at Sea producer Paul Crompton said Spall arrived at Chatham Marina on the barge on Thursday, where they would remain for two or three days.
Spall and his wife, Shane, have been sailing their Dutch barge around the British Isles for the BBC Four series.