‘Don’t Rock The Boat’ stars are set to face 40-hour "shifts" in the vessel.
The ITV show is being billed as one of the most arduous programmes in British TV history, with the celebrities facing energy-sapping shifts on the boat followed by gruelling "land challenges".
A source said: "The celebrities do have to put in huge shifts on the boat, sometimes as long as 40 hours.
"But they are allowed back on land and they often don’t restart from where they finished up. They’re not rowing the entire length of Britain but bits of it in short, gruelling bursts.
"When they’re not on board, the boat is tugged along by another vessel and they’re reunited a day or so later."
ITV bosses are insistent that the time on land will not be a break for the contestants.
Instead, members of each team will face an on-land challenge while the others row the boat.
An ITV source told The Sun newspaper’s Bizarre TV column: "This is not just a rowing show. They stop and compete in terrifying land challenges.
"The route has had to change because of the weather, including Storm Ellen. The weather conditions have been worse and they experienced stronger currents than expected.
"There was extreme sickness on both boats. Duty of care is the first concern for our novice contributors. We are guided by our independent race director as to what is deemed safe and this will all be shown in the programme."
The upcoming series will see 12 celebrities – including former ‘Coronation Street’ star Lucy Fallon – row the 650-mile English coast.
The show will be hosted by Andrew ‘Freddie’ Flintoff and will air in the autumn.
‘Love Island’ star Kem Cetinay was originally due to take part but quit after just one day of training.
A source previously said: "Kem was as keen as anything to take part in the show when he first signed up. He loves keeping fit and the idea of rowing 650 miles with a load of other stars seemed like a good laugh.
"The 12 celebs were split into two teams and had to compete against one another. But when it came down to the actual task the prospect of it proved too much and he left on the first day of training."