A German fisherman caught more than he bargained for when he cast his line into the river Isar this summer. But there was no way he was going to haul his prize out of the water with a simple fishing rod because what’d he snagged was a car that had laid on the river bed for more than 35 years.

Having spotted something unusual resting at the bottom of the river, the angler informed local police in Dingolfing-Landau, close to the BMW plant that has been cranking out 5-Series sedans since 1972. Police then deployed a diving robot to identify that the angler’s find was no sub-aqua monster but a classic first-generation E12 5-Series.

Related: 8 Generations Of BMW 5-Series, Which One Did It Best?

 Anyone Lose A Classic E12 BMW 5-Series Because There’s One Playing Submarine For 35 Years
Photos Polizei Bayern

Once trained divers had secured the wreck a crane was brought in to lift it, and the hundreds of pounds of mud inside it, to the surface. The police were astonished to discover that the body of the car was remarkably well preserved, reasoning that being buried in the mud had actually helped protect the shell from the corrosion BMW fans know these Fives are prone to.

But they were also relieved to confirm, once they’d hosed out the mud from the interior, that there no human remains inside the sedan. TÜV roadworthiness data for the car expired in 1988, giving police an idea how long it had been in the river, but as for who the car belonged to and how it came to be there, no one knows. Although the 5-series was still wearing license plates, the related files had long since been deleted for data protection purposes and BMW wasn’t able to provide any information using the car’s chassis plate.

 Anyone Lose A Classic E12 BMW 5-Series Because There’s One Playing Submarine For 35 Years
Photos Polizei Bayern

Which means police are hoping that people with really long memories might remember a neighbor, friend or relative who owned a light blue E12 5-Series in the late 1980s and had it stolen. The shape of the bonnet and rear lights tells us it’s a post-’76 facelift car, and the engine shot shows a four-cylinder engine, which was fazed out in favor of an inline six on the 520 in 1977, so that narrows things down a little.

Or maybe not. The VIN plate says it’s a 520, but unless we’re mistaken that looks like a single-carb 518 motor. The four-cylinder 520s used the same M10 block as the 518, but came either with twin carbs or Bosch fuel injection, neither of which is on this car. So the mystery of this 5-Series, like the water it was found in, is very murky indeed.

 Anyone Lose A Classic E12 BMW 5-Series Because There’s One Playing Submarine For 35 Years
Photos Polizei Bayern