Swimmers trying to upturn the pontoon at Wellington's Oriental Bay have been warned they risk seriously injuring themselves.

It seems it's a challenge too good for many young swimmers to resist.

But Wellington City Council has warned that trying to flip over the diving pontoon in Oriental Bay can be extremely dangerous.

"Imagine hundreds of kilograms of platform with an anchor chain and metal handrail toppling down on you," council spokesman Richard MacLean said on Tuesday.

If you know these fun-bunnies, please ask them to never again flip our pontoon upside down. It is there for everyone to enjoy. pic.twitter.com/SgQ9n1f5Li — Oriental Bay (@OrientalBayNZ) January 22, 2018 His warning came after a group of swimmers were seen trying to upturn the raft on Monday evening. READ MORE: Carter Fountain springs back to life eight months after breaking "It's happened a couple of times this year, which is bit of a concern considering how easy it would be for someone to be seriously hurt." And THIS is how a bunch of idiots flip the @OrientalBayNZ pontoon. Serious injury could occur. If any of these are YOUR idiot, please have word? pic.twitter.com/iD25IPPbeD — Alan (@BabeAtSea) January 22, 2018

Apart from the safety risks, flipping the pontoon was also annoying for other swimmers who wanted to use it, if it was not put back upright, he said.

"All we're trying to say is go out there and have fun on the raft, but just chill out, young people. Stop turning things upside down."

Securing the raft so it could not turn over, possibly by attaching extra mooring chains, was an option for the council to consider, he said.

"It's something we can fix if need be. The same thing used to happen at Island Bay until we fixed the swimming raft's design so that it couldn't flip over.

"Whether anything will be done by the end of the summer, we'll have to talk about that in the next few days.

"In the meantime the message is, 'Please don't do it'."