Singer Jade Thirlwall says working on the official song for BBC documentary Blue Planet III is "one of the best things" she's ever done.
The former Little Mix star worked with legendary composer Hans Zimmer on Into The Deep (Seas Cry), a piece created for the launch of the series narrated by Sir David Attenborough.
Thirlwall, who debuted the track on BBC Radio 1's Breakfast Show, told host Greg James working on it was a "very special" experience.
Blue Planet III is due to air this autumn, but an official release date is yet to be announced.
During her breakfast show appearance, Thirlwall said Blue Planet, which focuses on the life of our seas and oceans, was her favourite TV show.
"When this opportunity came in, I might have shed a little tear," she said.
"I was just so buzzing to be a part of something so special.
"I'm a huge David Attenborough fan, I love the planet, I love the oceans. It was so magical getting to write a song all about that."
Thirlwall said the track, which mixes her striking vocals with Hans Zimmer's signature orchestral builds, was written to be "celebratory".
She said footage captured by Blue Planet III crews played in the background as she worked on creating the theatrical piece.
"The song is about the oceans and how special they are, hope, fighting the good fight to make the world a better place," she said.
Thirlwall also said she was "busy writing" a second album after a busy summer of festival performances, including slots at Reading and Leeds in August.
It's not the first time a big artist has worked with Hans Zimmer to create a track for the BBC's nature programmes.
Singer RAYE and Bastille frontman Dan Smith have previously collaborated with the Oscar-winner.
George Fenton, another key Blue Planet composer who'd worked on other BBC nature documentaries, as well as classic films such as Gandhi and Groundhog Day, died this week at the age of 76.
