They may have no idea how American football works, but that won't stop Australians from trying to get their ads shown at the Super Bowl.

2016 marks the third year in a row that an Australian has been a finalist in Doritos' "Crash The Superbowl" advertising competition, in which directors compete to have their commercial for the snack shown during the event, starting with the infamous Finger Cleaner ad of 2014.

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Despite the run of luck in the finals, no advertisement from Down Under has yet been able to win overall. Melbourne-based director Peter Carstairs is hoping to change all that with his ad, Ultrasound, which is in the top three of this year's competition.

Should Carstairs win, his ad will be screened at the most watched television event in the world, reaching more than 114 million viewers in the U.S. alone.

"It is massive. It's so massive that it's a bit hard to comprehend to be honest," Carstairs told Mashable Australia. "As filmmakers here, you don't often have much of an audience, particularly in Australia, so to be screening to the world's most watched television event is a bit of a mind-bender."

It's the kind of exposure that's once-in-a-lifetime, and comes with the opportunity to shadow a Hollywood director. This time, it's Zack Snyder, director of 300 and Batman v Superman: Dawn of Justice.

"These things just don't come up in Australia," Carstairs said. "You can't just wander into Warner Bros. Studios and ask to speak to Zack Snyder."

Carstairs has dabbled in advertising and television, and decided he wanted a piece of the action after watching other Australians make the finals. For his ad, Carstairs collaborated with two writers, Heath Collins and Liam Jenkins, alongside production company Mr Smith.

"We were just throwing around about a bunch of ideas to give us the best opportunity for comedy," Carstairs explained. "We whittled the ideas down to a couple, and this one was the strongest. At first, we didn't have the ending. But once we had it, we knew it was the one."

Unlike previous Australian-made Doritos advertisements, Ultrasound features only American accents. A "conscious decision," despite the Australian actors, to ensure the ad would appeal to the American market.

Carstairs said his team were "all pretty incentivised to win it," with the US$1 million (A$1.4 million) prize to be shared among the cast and those involved in the project, were they to win. The film's small budget came directly out of their own pockets.

The choice of finalists came down to judges and merit, but Carstairs' fate now lies entirely with a public vote. The most amount of votes wins the competition, with entries closing Jan. 31 and the winner announced on Feb. 7.

"Although ours has been seen a lot, it doesn't necessarily convert into votes. So I'm trying to convince people to vote as much as they can," Carstairs said. "If we do win, we'd be the first outside the U.S. to win it. That would be really exciting."