Thieves have stolen up to $30,000 from a theme park wishing well near the Victorian city of Geelong.

Police say the thieves broke into Fairy Park, at Anakie, on Sunday night, and stole the coins that had been in the wishing well for up to eight years.

Detective Senior Constable John McKinnon says shops and banks should be on the look out for anyone trying to cash in large amounts of rusty coins.

He says the thieves brought in a pump to drain water from the well.

"The offenders have forced their way through the fence and drained the water, which is about two metres deep," he said.

Detective Senior Constable McKinnon says the owners believe the well may have contained up to $30,000 worth of coins.