Officers swooped immediately and used a broom to detain the trespasser.
Senior Sergeant Dave Houston said the owner of the car had been slightly confused when he returned to find a group of officers searching underneath it.
Sgt Houston added that little Steve had had a “lucky escape” and "could have been killed" if the had driver sped off without noticing what was hidden beneath his car.
In custody: The seal pup was kept in police cells overnight
Wellington District Police
He told Stuff NZ: "He could have been squashed.”
Despite being a "little bit bitey", Steve was kept in police custody until he could be bailed out by the Department of Conservation.
They now plan to release him back into the sea off the south coast.
According to conservation workers, the pup is likely to have been left to live independently by his mother.
It is reportedly common for seal pups to get very tired during their first few days of freedom.