In a shocking act of vandalism, the wooden benches were pulled up and thrown down the banks of the River Adur where they were found partially submerged in the water.
They are part of the tribute to the 11 men who died when a 1950s military jet crashed on to the A27 during a display at Shoreham Airshow in August 2015.
It has been funded by local councils and businesses.
A spokesman from Sussex Police appealed for anyone with information about the vandalism to come forward.
He said: “Police have been made aware of damage caused to two benches dedicated to the victims of the Shoreham Airshow disaster.
“The matter is being taken seriously and enquiries are ongoing.
“Anyone who saw what happened or who has any other information about the damage is asked to contact police online or by calling 101.
“We would always encourage people to report instances of criminal damage to police so we can investigate and respond effectively.”
Members of Adur District Council’s maintenance team, together with two members of the public, managed to rescue the benches from the river.
The council said they will be secured back into the ground later this week.