Lincoln Beswick,18, pleaded guilty to theft at the Ballarat Magistrates' Court on Monday.

Police prosecutor Senior Constable Ben Jones told the court four teenagers were swimming at Lake Calembeen in Creswick on December 19 when they realised their bags they had left under a tree on the bank were gone.

The bags contained iPhones and a credit card.

Police spoke to the victims, who said they had used the Find My Phone tool to locate the phones and bank records showed the card had been used at the Shell Petrol Station.

CCTV footage at the petrol station showed the accused making a purchase.

Senior Constable Jones said police arrested Beswick on December 27 after a short foot chase.

When interviewed by police, Beswick denied stealing the phones and the card.

Defence lawyer David Tamanika said Beswick was a 'confused' young man who was overconsuming alcohol.

Beswick was supported by his mother in court. The court heard Beswick would live with his mother on his release.

Magistrate Letizia Torres said it was important Beswick stayed with his mother in a stable environment.

"This is pretty serious offending," she said.

"It is just such a mean thing to take people's bags while they are having a swim."

Beswick was sentenced to 50 hours unpaid community work.

"That is less than I would have done because you have spent that time in jail," Ms Torres said.