Musicians, instruments, a stage... there are few things that might be considered vital if you were staging a music concert, and it's fair to say that air for the performers is usually one of them.

But Danish company Between Music, led by producer Sigrid Aakvik, disagrees. In their ground-breaking - or rather, breath-taking - production, AquaSonic, five singers and musicians playing custom-made instruments are submerged in specially-designed glass water tanks to deliver their performance.

"AquaSonic is the result of asking simple questions in the search for complex answers," explains Sigrid. "In 2004, I asked myself the question: 'Is it possible to sing in and under water?' This set off a long and very complex journey that lasted over a decade, challenging the 200,000-year-old human tradition of expressing music through the air.

"I asked: What does it do to us humans, when our norms and habits are fundamentally challenged? Can it help to find new answers, new understandings of who we are as human beings? Of our origins? Our existence? Our ability to invent, adapt, survive and evolve as a species and how we relate to our surroundings?"

As the culmination of the team's years of research into the exciting possibilities of submerged musical performance, AquaSonic premiered in the Netherlands in 2016 and is now a viral worldwide phenomenon. Perhaps fittingly, given the water theme that flows throughout this year's Malta International Arts Festival (MIAF), the next step on the AquaSonic journey will be to perform as the grand finale of this massive annual celebration of artistic innovation and interdisciplinary expression.

"We are really excited about this experience," continues Sigrid. "We usually present AquaSonic in indoor spaces, so it is fantastic to have the opportunity to present it in this outdoor site-specific venue, so close to the sea. Plus, this will be our first time in Malta, as well as the first time we perform AquaSonic on an island, so we are very curious to see the reaction of an audience that is used to being surrounded by water, and if it is different from inland audiences."

However, the logistics of mounting an entirely underwater production, in a foreign country, on a dry stage, is not without its challenges, as Sigrid points out. "AquaSonic has sent us on a crazy journey, and the challenges are many! But we have been able to solve each of the problems that arose through the input of many generous collaborators from very diverse fields, such as instrument builders, deep sea divers and experts in acoustics. The team in Malta at the MIAF have been very helpful logistically, while our artistic manager and composer Laila Skovmand has been the core person pushing this project forward and Robert Karlsson has pulled the strings collaboratively."

Through this collaboration with experts, the AquaSonic team were able to develop entirely new, highly-specialised subaqueous instruments including an underwater organ or hydraulophone, crystallophone, rotacorda, percussion and violin. Likewise, the singers also needed to perfect a distinctive vocal technique to be able to sing under water.

Beyond perfecting these new techniques, the five underwater musicians also had to overcome numerous obstacles to prepare for the performance - not least, the need to breathe. "These five musicians are the only ones in the world who can actually play these unique instruments, and it has demanded a lot of exhausting hours training in hot water. It is not possible to read notes under water, so all the music must be learned by heart - and they cannot see or communicate with each other. The only contact they have is via tiny in-ear monitors. They have also trained in yoga and with deep-sea divers, in order to control the breath and learn how to hold their breath longer, while ignoring their body's natural panic reaction."

However, all this work from both the cast and crew of AquaSonic has more than paid dividends considering the critical acclaim the concert has received from critics worldwide. Time magazine has described it as "eerily spectacular", while the New York Times said it was "spellbinding" and the Huffington Post called it "a sound that's haunting in the most beautiful way".

For Sigrid, however, the show is so universally important because of something far deeper that is shared within the human condition. "We have ideas that everybody can relate to in some way or the other. AquaSonic has so many strong symbols and narratives, both related to the mythological and psychological symbol of water, but also water has, in our day and age, become a symbol of climate change and the immigration crisis. But above all, despite our differences we all have one thing in common: that we spent our nine first months in water and heard our first sounds through a water filter. And through AquaSonic, we are able to hear those sounds again."

'AquaSonic' will be performed by Between Music at 9pm on Saturday 13 July, on the Main Stage on Boat Street (Il-Fossa) in Valletta. More information regarding The Malta International Arts Festival (MIAF) may be found by visiting www.festivals.mt/miaf.