A joint operation between Tasmania Police, Biosecurity Tasmania and Spirit of Tasmania staff, two cars were intercepted and searched as they disembarked the vessel in Devonport.

As a result of the search, detectives seized about half-a-kilogram of methylamphetamine from the vehicles, which has a street value of about $500,000.

A 31-year-old man and a 37-year-old woman were charged.

"This is part of an ongoing investigation which has resulted in more than 1.5kg of ice, with a street value of $1.5 million, being seized in less than three weeks," Detective Inspector Kate Chambers said.

"I'm confident that the excellent work undertaken by police and our partners has disrupted the activities of individuals who seek to exploit vulnerable members of our community for their own personal benefit."

Detective Inspector Chambers said the operation had removed more than 15,000 street deals from vulnerable Tasmanians and if the community worked together it could make a real difference to people's lives.

The man and woman charged will appear before the Devonport Magistrates Court at 10am.