While there were many nervous faces in the crowd, the Aspire Channel Relay 2014 Seagulls team showed no fear.
Karen Rees, of Christchurch, said: “We're swimming the Channel in September, so we're using today as a warm up.
“After it's finished, we'll keep going for another hour or so.”
John Gilbert, 66, of Alderholt, participated for the first time, and admitted feeling a bit anxious before the race started.
“I wanted to do an event like this so I could give something back,” he said.
“It seemed like a good idea at the time. Today I'm not so sure.”
Nikki Pardy and Jenny Charmoy, friends from Christchurch, had been taking dips in the sea to prepare themselves for the race.
“It's a great occasion,” said Nikki.
“I've watched it several times, and my husband's competed before. Life's all about new experiences.”
Tim Spirit, 55, travelled to Bournemouth from Brussels in Belgium in order to take part in the swim.
He said: “I'm taking part today because the BHF do so much to help people with really serious health problems - they're an excellent charity.
“It's a way for me to give something back. My son did this last year, and he didn't have a wetsuit on and almost gave himself hypothermia, but he said it was a great event and he'd really enjoyed it. It was my turn to have a go.”
Around £150,000 was expected to be raised in donations through the challenge.
Lesley Maynard, of Salisbury, said she felt “slightly apprehensive” before the starting pistol sounded.
The 71-year-old added: “I'm doing this because I'm in my 70s now, and I want to make sure that I stay fit and don't need any help from the wonderful BHF myself.”
The event is now in its 24th year, and is the biggest charity swim in Europe.
Last year's event raised over £100,000 for charity and saw 1,800 swimmers take to the water.
All those who complete the swim will be presented with a medal, and money raised will fund essential research into heart disease, the single biggest killer in the UK.
More than £150,000 is expected to be raised for the British Heart Foundation
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