The fake commercial appeared almost identical to Apple's real poster advertising with images of the iPhone on a white background accompanied by neat text.
"Update to iOS 7 and become waterproof", the poster read.
"In an emergency, a smart-switch will shut off the phone's power supply and corresponding components to prevent any damage to your iPhone's delicate circuitry," it explained.
At the bottom of the poster was a promise that "waterproofing [is] covered by Apple's warranty policy".
After being shared on social media sites by users encouraging people to try the new feature soon angry complaints appeared from those fooled by the joke.
"Whoever said ios7 was waterproof **** you," wrote one user on Twitter. "Wtf iOS7 isn't waterproof!! Now my phone's at the bottom of the river," another said.
The prank is understood to have been started by controversial forum 4Chan which has a chequered history of hosting faked material.
