The train ran off the end of an elevated section of track but, in a bit of catch of the day luck, avoided crashing to the ground after it got caught several metres in the air by the two tail fins of the structure.
The architect behind the design, Maarten Struijs, told Dutch broadcaster RTL he was pleased his marine mammal had accidentally doubled up as a life saving monument.
"I’m surprised it’s so strong," he said. "If plastic has been standing for 20 years, you don’t expect it to hold a metro carriage."
The miraculous marine moment caused such a stir locally that authorities had to urge sightseers to stay away citing Covid restrictions.
All the same more than 50 people were at the scene late Monday morning as engineers tried to work out how to safely haul in the metro carriage.
"A team of experts is investigating how we can make it safe and get it down," Carly Gorter, a spokeswoman for the local security authority, said in a telephone interview.
"It’s tricky," she added.
The company that operates the metro line said the driver was uninjured and there were no passengers on the train.
The station, in the town of Spijkenisse, on the southern edge of Rotterdam, is the final stop on the metro line.
Authorities have launched an investigation and the driver has been interviewed as part of the probe, the Rijnmondveilig security authority said.