Emergency services will gather at the River Tay for a training exercise today to test their response to a major incident.
Members of the public are being urged not to panic if they spot what looks like a body in the river from 6pm.
Two boats will be in the water near Perth to simulate a crash.
Dummies will also be in the water between Moncreiffe Island and Newburgh and actors will be on the shore.
Locals have been told to expect to see emergency workers from nearly all services, along with Dundee Airport Fire Service and NHS Tayside staff.