The River Stour should return to its normal level over the next few days after a specialist dive team removed a blockage.
A blockage at Cornard weir had caused a control gate to be jammed open meaning levels upstream in and around Sudbury were around six feet lower than normal, with 10,000 fish being rescued.
In some areas, such as the cut off by the Quay Theatre in Sudbury, only shallow puddles remained.
A spokeswoman for the Environment Agency said: “A specialist dive team trained to study this type of structure was able to come early today to have a look at what may have caused the automatic control gate to jam open. The dive team was able to raise the gate freeing the debris and allowing the gate to return to normal operation.
“Now that the gate is operational again the river levels should return to normal over the next couple days. We monitored the river levels throughout the incident and moved approximately 10,000 fish to deeper water.”
One Sudbury resident told the Free Press he had not seen the river like it in 80 years of living beside it.