The incident yesterday (Wednesday) resulted in army bomb disposal experts being called to the beach.
Skegness Coastguard had been responding to reports of a possible upturned boat at Ingoldmells point.
The emergency service said: "We arrived on scene and quickly identified it as pipe work from the beach work being carried out.
"Skegness inshore lifeboat was also tasked and double confirmed the object. The first informant did exactly the right thing calling 999 .
"Whilst on scene a member of the public who had been metal detecting on the beach approached us as they had found an unfired bullet .
"We contacted EOD and they attended the incident. While they were on route we put a cordon in place and kept the public at safe distance.
"On arrival the EOD collected the bullet for safe disposal."
* In an emergency on the beach, call 999 and ask for the Coastguard