People are being told not to worry if they see an increased emergency service presence at the Elizabeth Terminal.
Jersey's government is practising the response to a major incident with 'live incident' at the harbour from 9:00 am until 2:00 pm today (8 October)
The Jersey Resilience Forum - which includes Ports of Jersey, Customs and Immigration and all emergency services - will be involved.
Exact details of the scenario have not been released, but it will involve setting up a 'Survivor Reception Centre'.
Volunteer actors are being used to play the part of distressed victims who look like they need medical attention.
Officials want to reassure people that it is just part of the exercise.
The terminal will be closed to the public at 8:30 am, but no passenger sailings are scheduled so there will be no travel disruption.

Invite to 'Sponsor a Brave Bear' for families facing off-island treatment
Travel problems persist for some Jersey residents
The solar eclipse in Jersey: All you need to know
£1.2m in fines for missed Income Tax deadline
One in eight Jersey heatwaves has happened this year
Hydration breaks to be introduced at Battle of Flowers
Nurturing biodiversity key to climate resilience
Record amount raised in 2026 Jersey-France challenge