Twelve yachts that will travel around the globe have set sail from Liverpool.
More than 700 amateur sailors - led by professional skippers - are involved in the 11th edition of the Clipper Round the World Yacht Race.
They are expected to finish in Liverpool on 28 July next year.
Race co-founder Sir Robin Knox-Johnston, who was the first person to sail solo and nonstop around the world, said: "This requires give and take - people aren't used to that these days."
Thousands of people lined the waterfront as the fleet paraded on the River Mersey before starting the first leg of the race, which will end in Punta del Este, Uruguay.
At more than 6,400 nautical miles, the initial stage is expected to take 35 days - making it the longest opening leg in the 21-year history of the race.
The sailors either travel on certain legs of the race or navigate the whole 40,000 nautical miles. The ships will visit other cities including Seattle, Cape Town, and Qingdao.
Sir Robin said: "They are going to have to settle down very, very quickly and get used to the fact that - for four or five weeks - they are in their little capsule and the nearest humans, apart from the other boats, will probably be the space station.
"The biggest challenge they face isn't actually the sailing, it is getting used to living in a very tight and confined community."
The race happens every two years. In 2015 it was overshadowed by the death of Andrew Ashman, from Kent, who suffered a neck injury during the first leg.
His death was the first in the race's 20-year history but was followed by the death, later in the same race, of Sarah Young, from London, who was washed off the deck during the Pacific leg.
Sir Robin described the deaths as "upsetting", adding: "These crews are aware of the need to take precautions all the time and never ever relax your guard.
"Providing they do that they will come home safely."
'A great way of to kick off retirement'
Among this year's participants is Tessa Hicks, from Wiltshire, who expects to celebrate her 60th birthday on the Southern Ocean.
Having never sailed before race preparations, she said: "I'm getting close to retirement so it seemed like a great way to kick off my semi-retirement.
"I went to medical school in my 40s when my children were all teenagers so I like to be busy and have challenges so why not the Clipper Race?
"If you want to do something badly enough you will find the time to do it and make it work."