The mad cap idea is based on the Finnish Kaljakellunta (pictured above), meaning "beer floating", and would see huge crowds take to the water in Newcastle.
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Police have expressed grave concerns about drinking a "significant amount of alcohol" in vessels that were not "appropriate".
"The River Tyne is not a countryside stream," a spokesman said. "The current is strong, there is a lot of debris and a number of vessels use the waterway every single day."
But Kieran Chapman, 21, who advertised the event, says it will go ahead on July 1. "You have a right to go into the water," he said.
"But it is obviously very dangerous without a life jacket. You always get the idiots. It may be upstream where the river is not tidal.
"The idea is a mini booze cruise. We don't want excessive amounts of alcohol but the dinghies are built to float on shallow rivers.
"This is not an event I am creating, otherwise I am eligible if anything goes wrong. What I am saying is: 'I am going down the River Tyne in a rubber dinghy and you are welcome to join me'."
He has been rescued twice on the Tyne, once in an inflatable which 'ran out of fuel' 18 months ago , and last year in a £1200 speed boat.
A bridge crossing the River Tyne
He added: "I am really grateful to the RNLI. They saved me twice. When I was in the dinghy, I just managed to stay in one place as we were up against the tide.
"In the speedboat, a prop broke. I had to sell it as I joined the circus.
"I ran away to join Charles Chipperfield Circus as a clown, which is what I have always wanted to do.
"I was a mechanic, and when I handed in my notice, the manager said 'you cannot be serious'.
"I am an apprentice clown. They have just got a little clown car for me."
Kieran, of Dumpling Hall, Newcastle, wants the Geordie version of 'Kaljakellunta' to become an annual event and is planning a 'mini music festival' for the end of the cruise.
His brother Ryan Lambert, known as Tasker, is due to host as a DJ. It is £20 a ticket, with 30 per cent of the profit going to the RNLI.
The event's Facebook page, which has 12,000 likes, recommends participants wear armbands and life jackets and stay on their vessel at all times "to eliminate accidents".
Kieran added: "We may move to water which is not tidal, because the police have safety concerns. I totally understand that."
But Northumbria Police still have 'significant concerns'. "Alcohol impairs judgement, reaction time and co-ordination," said a spokesman. "It contributes to 20 per cent of all adult drowning every single year. That figure rises to 40 per cent in people aged between 15 and 29.
"We understand people want to have fun but our absolute priority is to ensure the safety of the public."
Organisers of such events are supposed to approach all the relevant authorities — which have the power to cancel them — to seek permission and show that appropriate safeguarding measures are in place.
Newcastle City Council said that it had not been approached for permission for the "incredibly irresponsible" event. David Leach, of the local fire service, urged the thousands who "liked" the page not to go, saying:
"Rubber dinghies on open water and alcohol are a dangerous mix, and there is a real potential for someone to be injured or even drown."