Four teenagers have been found alive after going missing in waters off Victoria’s Mornington Peninsula.

The 18-year-old woman, two 18-year-old men and a 19-year-old woman were found on Swan Island on the Barwon Peninsula on Tuesday morning, on the opposite side of Port Phillip Bay

The group had been last seen using inflatable paddle boards off Rosebud Beach on Monday, 20 kilometres from where they were eventually found.

Their belongings, including phones and IDs, were found on the beach by a passerby about 8pm, sparking alarm.

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A huge search was launched overnight, including the police helicopter, ambulance choppers, water police and local rescue boats. It was halted at 4am due to deteriorating conditions before resuming at 7am on Tuesday.

A man who said he was the father of one of the boys told Seven’s Sunrise program on Tuesday the teenagers had just completed their final school exams and and gone to Rosebud for an end-of-year celebration.

The teenagers were found on Swan Island, on the western side of Port Phillip Bay, after drifting from Rosebud, on the Mornington Peninsula. Image: Google Maps

He said the teens’ families were disappointed the overnight search had been called off.

“We’re very much frustrated. We have been waiting here since yesterday evening,” Jack Shi told the show.

“A lot of people are helping. We really appreciate that but we just hope it can be noticed by more people.”

The condition of the four young people is not yet known.

-with AAP