The seven-man Toby Wallace boat – skippered by Simon Chalk of Loggerheads and with Steve Harpin from Cound – and the five-man Oystershack team, which has Telford businessman Christophe Legeais on board, left Gran Canaria on Monday and covered more than 100 miles in their first day.
But they already feeling the effects of rowing for hours on end at sea, according to challenge organisers.
Both teams are hoping to break the 32-day world record by rowing 3,000 miles and reaching Barbados before 10am on Boxing Day.
Gemma Chalk of Oceanus Rowing, which has organised the challenge, said the first 12 hours on-board both boats were quite interesting and that Toby Wallace was currently in the lead.
She said: "Only three members of Toby Wallace have not been sick yet. The rest of the crew are coping but not completely over it just yet.
"The Oystershack also had a fair amount of sea sickness, where only skipper Paul Williams was fine, however he did get hit by the first flying fish of the trip to make up for it.
"Despite the sea sickness on-board both the boats, they are pushing hard and everyone was happy to be on their way.
"The weather is changing for them in the next two days which may drive both boats more south until the weekend. They are hoping to keep up their mileages towards Barbados as best they can in the meantime."
The two crews were initially delayed for a fortnight because of bad weather. They were further delayed on Sunday when 100 sailing boats set off in their own race.
Mr Chalk, 42, has rowed the Atlantic six times while Mr Harpin, 47, is using the challenge to raise money for the Bickerstaff Endoscopy Unit at Telford's Princess Royal Hospital.
The teams can be tracked at during their journey on organiser Oceanus Rowing's website www.oceanusrowing.co.uk/atlantic-ocean-rowing