Two adventurers who scaled an iceberg moored in the ocean just off St. John's say what they did is risky, and shouldn't be attempted by people who don't know exactly what they're doing.

"Because it's there, we have to climb it," said St. John's resident Justin Emberley, who astonished onlookers on Wednesday afternoon when he and friend Kevin Le Morzadec, who is visiting from France, climbed the berg.

"We have been rock climbing for years. We do know what we are doing," said Le Morzadec, who last year climbed an iceberg near St. Anthony, on Newfoundland's Northern Peninsula, while visiting Emberley.

"We're not just like crazy people going in the water and climbing. We do know the risks. We do know that if we go on it, it can break and we can die."

Emberley and Le Morzadec swam to the berg, which is moored near the famously picturesque harbour of Quidi Vidi, an enclave in the east end of St. John's. [They recorded their exploits on video, a version of which is posted above. The video also includes brief footage posted by YouTube user newfoundsander that features the pair jumping off the iceberg.]

Emberley and Le Morzadec, noting that the berg had not moved in two days, felt comfortable it was safe to proceed.

Yet both men said they would not recommend that any novice climb an iceberg.

"I would probably say not to do it," Emberley said.

Le Morzadec added, "I wouldn't tell to anybody, 'Oh you should come with us.' ... Yes, it is dangerous."

An iceberg can roll at any time, throwing tonnes of ice underwater in a matter of seconds. Icebergs are popular draws in many Newfoundland communities during the spring and summer, but tour boats often keep a respectful distance for the safety of their passengers.

"It is extremely fun. If it wasn't for the fact that it could roll and you will die, I would do it all the time," Emberley said. "But [there] just comes a point that you cannot climb it anymore."

St. John's resident Jerry Curtis was one of several onlookers who saw the pair climb the berg.

"We were totally amazed — either they're very brave or very foolish," Curtis told CBC News.