A crew member on a ship anchored off Western Australia is alleged to have jumped overboard and swum ashore to avoid Covid-19 quarantine.

The 37-year-old Vietnamese man worked on a bulker that had berthed at Albany Port in the southwest of the state on Thursday, local police said.

It is alleged the man jumped into the water on 9 January and swam ashore, in contravention of the state's controlled border directions and the maritime crew directions.