Human submarine Tanya Streeter took a final deep breath and slipped silently into the blue waters of the Caribbean.

She emerged, three minutes and 38 seconds later, a world beater.

The former Roedean schoolgirl, who took up the sport of freediving after graduating from Brighton University, broke both the men's and women's depth record as she descended to 400ft without the help of any breathing apparatus.

Using a weighted sled, she dropped down a line dangled from a boat off the Turks and Caicos islands, 575 miles south-east of Miami.

After a signal from her support team telling her she had reached her target, she kicked away the sled and swam back up to the surface with fins.

As she burst out of the waves, gasping for air, she gave a thumbs-up and declared: "It feels really good!"

Relaxing with a glass of champagne Tanya, 30, whose family live in West Sussex, said: "I guess it's just in the psyche of an athlete - you have to be confident in your abilities. But it was a hard dive.

"I'm really happy but my greater emotion is just relief because I set myself a very hard target with this dive.

"Everything went pretty well considering it's a really long way to swim down and back up while holding your breath and expending a lot of energy.

"I'm just happy I lived up to my expectations."

She added: "When I got to the bottom the guys broke into a rendition of Crocodile Rock. I heard them say 'It's a new world record' but they were on helium, so they had squeaky voices."

She smashed the previous women's record which stood at 311.7ft and was held by Cuba's Deborah Andollo.

And she also broke the men's record of 393.7ft set by Belgian Patric Musimu - making her the only woman in any sport to have beaten a male world record.

Tanya, who met future husband Paul Streeter while she was working at the Black Horse pub in Rottingdean, said breaking the records would help in her work promoting environmental organisations the Whale and Dolphin Conservation Society and Coral Reef Alliance.

The last time a woman tried to set a freediving depth record ended tragically with Audrey Mestre's death in October off the Dominican Republic.

But Tanya, who now lives in Austin, Texas and has held world records before in the sport, was confident and praised her husband and manager for his support.

She said: "There was a time when even submarines couldn't go as deep as I went. But I've never seen it as a case of conquering the depths or beating the sea.

"I look on it as a privilege to be accepted by nature's most powerful force."