UPDATE 1:16pm A boat is being towed back to Dawesville after activating an emergency beacon around noon.
A police spokeswoman said people on board the vessel activated the Epirb after a mechanical breakdown and the vessel was in a location with no radio or phone coverage.
She said the vessel was now under tow and returning to Dawsville.
The RAC Rescue helicopter, a Water Police vessel and two other vessels headed to where an Epirb was activated around 12.15pm.
A police spokesman said RCC Australia had advised Water Police of an Epirb activation approximately 20 nautical miles west of Dawesville.
The helicopter and two rescue vessels have been stood down.