A more than one thousand watched on as the quirky concept became a reality in the waters of NSW's Tumut River on Saturday.

The paddled pumpkin wasn't just any old vegetable, rather a prize-winning pumpkin grown by horticultural scientist and Tumut local Mark Peacock, which recently took out first place at the Sydney Royal Easter Show.

After harvesting thousands of seeds, worth $50 a pop, Mr Peacock was stuck on what to do with the massive vegetable, which weighed 412 kilograms.

Enter Tumut thrill-seeker Adam Farquharson a friend of Mr Peacock's, who asked if he would consider turning the pumpkin into a boat so it could be paddled down the river.

The former Tumut Valley Canoe Club president had heard of pumpkins being paddled in rivers often in America and had wanted to try it for some time now.

"I tried growing one and it was a hilarious failure," Mr Farquharson said.

Mr Peacock said while an unexpected request, it was one he could not pass up.

"He's a random bloke who does random stuff," he said of Mr Farquharson.

"I went and helped them unload the pumpkin and drag it into the river on Saturday.

"About 1500 people showed up to watch and the ambulance [paramedics] also showed up - we didn't tell them - half the town just showed up to watch."

Mr Farquharson was also surprised by how many people were invested in act.

"I'm a massive fan of shenanigans," he said.

It wasn't all fun and games though, with being inside a pumpkin not the most thrilling of experiences.

"They're really slimy," Mr Farquharson said.

"When I first hopped in I thought it was quite icky."

With his wing-man Duncan Watt in a kayak keeping an eye on him while in the river, Mr Farquharson was able to successfully live out his pumpkin dream without chaos.

He paddled down the river for 1.6 kilometres without capsizing. In preparation, he had canoed down the river the day before to ensure it was clear.

The keen boat captain, who named the pumpkin boat Cinderella, had expected to make quite the spectacle of himself with fast-flowing water to contend with and confidence in the boat's structural integrity lacking.

Mr Farquharson said people had told him he was crazy for wanting to do it in the Tumut River given its flow.

With assistance from Mr Peacock, the pair retrieved the pumpkin from the river after the once-in-a-lifetime ride.

Mr Peacock then shared pieces of his pumpkin with those gathered after the boat ride was done.

"We had to cut it up to get it out of the water, half of the people took some pieces of the pumpkin home - I presume to cook and eat," he said.

Mr Peacock himself had a nibble and was surprised to find the pumpkin was quite a good eat.