Until late last month, to the best of my knowledge, there had never been a major Australian art prize awarded to a performance piece. It had to happen eventually, and the breakthrough moment came at the Art Gallery of South Australia, where local woman, Ida Sophia, took out the $100,000 Ramsay Art Prize, for her work Witness.

It seemed a daring decision at first, and even now I can imagine readers huffing and puffing in indignation, but as one wanders around the exhibition, Sophia emerges as a very credible winner.

The Ramsay takes its lead from the Moet et Chandon award for artists under the age of 35, which ran throughout the 1990s. The current prize is open to artists up to the age of 40, generously allowing contestants another five years to define themselves as “young”. It’s a slightly arbitrary figure anyway, as some artists mature early, some late. Emily Kame Kngwarreye was in her late 70s when she painted her first pictures!

In its fourth iteration, this biennial prize is gathering momentum. The show offers an overview of emerging talent from all over Australia – a potential shopping list for curators and collectors. While a handful of the 27 finalists have already featured in major exhibitions and collections, most are relative newcomers. The prize is being funded in perpetuity by money provided by the late Diana and James Ramsay, two of Australia’s most generous patrons of the arts.

Witness consists of a video of a mock baptism, set in a lake in regional South Australia, with the wonderfully biblical name “the Pool of Siloam”. For 12 long minutes, the artist is dunked under the water by another artist, playing the priest. It’s gruelling to watch, as there are many moments when Sophia is gasping for breath as she is shoved back down into the pool. It’s hard to imagine how physically and emotionally draining this process must have been, especially when one learns the film was made in a single take that lasted half an hour.

It feels as if we are watching someone being water-boarded rather than baptised. It conjures up thoughts of all the suffering and privations people go through in the name of religion, where the mortification of the flesh is often the first step towards the purification of the soul. The work is based on the artist’s childhood memory of watching her father undergo a “profound baptism”, feeling resentful that he apparently loved Jesus more than he loved his daughter.

In this sense, the work is an exorcism, banishing those selfish thoughts while trying to experience the same sensations felt by her father. If it resembles a self-inflicted torture session, this is not unusual for the “endurance” school of performance art, most closely associated with Marina Abramovic. Sophia has already studied at one of Abramovic’s performance boot camps, in Greece, and has imbibed the steely attitude one needs to succeed in this difficult field.

The intensity of Sophia’s work makes many of the other entries seem light and superficial, so it’s best not to venture direct comparisons. Another striking video, Demarcation by Jacobus Capone, provides a panoramic view of a massive glacier in Norway. Across the edge where the ice floe meets the sea, we see the ant-sized figure of the artist tentatively walking the line. In this film, the self is submerged in the vastness of nature and the looming threat of global warming. The glacier is a breathtaking sight, but also cold and ominous. It’s a contemporary reflection on the Romantic concept of the Sublime, in which beauty is always tinged with fear and anxiety.