A surprise marriage proposal on Shark Tank caught everyone off guard.

There was a proposal of a different kind on Tuesday night’s episode of Shark Tank, when a Melbourne cafe owner asked his girlfriend and business partner to marry him.

Luke Lucas and Chrissy Glentis were on the show to persuade the sharks to invest in their speciality food brand Foddies – which caters to people who have intolerances and follow a diet low in fermentable, oligosaccharides, disaccharides, monosaccharides and polyols – commonly known as FODMAP.

However, what Chrissy didn’t know was that Luke had another life-changing pitch to make – this time to his partner of two-and-a-half years.

Listen: One of the sharks dishes out some stellar career advice.

After the pair made a deal with shark Janine Allis – who bought a 40 per cent stake in their business for $100,000 – Luke announced that he had “just one more thing” to say before turning to Chrissy.

“Without you, none of this would be possible. I can’t even imagine a life without you, frankly, I don’t want to. I want to spend the rest of my life with you,” he said getting down on one knee. “Chrissy, will you marry me?”

The 27-year-old replied yes to the delight of everyone in the room, with the sharks quick to congratulate the pair.

It was a dream ending to a high-stakes day, but Luke told Mamamia it may not have happened if the pair hadn’t managed to secure a deal – something that looked likely when all four Sharks pulled out before Janine made a final offer.

"I don't think there was a back-up plan. I hadn't thought about not getting the deal... If it hadn't have happened I just would have rolled with it," the 30-year-old said.

"I was definitely more nervous about the proposal than the business pitch."

The former financial adviser told Mamamia that he had been planning the proposal since the couple, who met in August 2014, first applied for the show.

"When we were applying I remember thinking if we are able to get on, I think I probably will (propose)," he said.

"The business has become such a big part of our lives. We started it five months into our relationship... I saw this as a good way to bring the two together.

"And then when I thought as well that I get the opportunity to propose to the woman that I love on national TV, I can't say no to that."

Meanwhile, Chrissy had "absolutely no idea" what her partner had planned, with her attention firmly focused on their shared business.

"He completely caught me off guard. It was such a shock. It was amazing," the former nurse said, adding that Luke insisting on keeping his jacket despite the warm temperature of the room didn't tip her off.

The engaged pair told Mamamia that Foddies had expanded since they appeared on the show and was their primary focus at the moment, while wedding plans have been put on the backburner.

"When we do it we want to do it properly... We're thinking the end of next year would reasonable," Luke said.

Married readers, where did you or your partner propose?