THE Clyde Tunnel has been transformed into an underwater world of mystery and adventure as part of a creative event.

The cycle path and pedestrian walkway has become a subterranean adventure full of kinetic sea creatures lurking in tanks, plants, light installations and music.

The spectacle is part of the Sonica arts festival.

The world premiere of the interactive event, called Portal, was presented by Glasgow-based artist Robbie Thomson in association with award-winning local arts house, Cryptic.

Cryptic associate director Alex Menzies created a unique and audiovisual journey through the tunnel, which marks its 55th anniversary of connecting the city this year.

Other locations getting in on the act for Sonica 2018 are George Square and the Charles Rennie Mackintosh tower at The Lighthouse.

George Square will play host to giant, semi-intelligent seesaws for the Scottish premiere of Madeleine Flynn and Tim Humphrey's Pivot, which will see built-in voice communicators poke, question and counsel audiences as they play on the aparatus.

And Visaurihelix by Louise Harris will take an interactive, audiovisual installation based on the geometric forms of Charles Rennie Mackintosh's architecture to The Lighthouse.

The Cryptic events are all free to attend and are part of Festival 2018, the cultural programme which is running alongside the Glasgow 2018 European Championships.

Cathie Boyd, Cryptic’s Artistic Director, said: "I’m thrilled that Cryptic’s Sonica is back with a summer of extraordinary free art across Glasgow.

"Our two collaborations with Festival 2018 are interactive treats for all ages - people will be able to re-discover their inner child on the delightful intelligent see-saws of Pivot and see the Clyde Tunnel transformed into an otherworldly spectacle in Portal, thanks to Robbie Thomson.

"We also can’t wait to experience the premiere of sound and audiovisual artist Louise Harris’s Visaurihelix, which will turn one of Mackintosh’s iconic Glasgow buildings into a sonic sculpture.”

Portal runs between tomorrow and August 12.