The bomb disposal squad were called after a family discoverd three hand grenades at the beach.
Amanda Lockey almost trod on the seventy year old No. 36 Mills Bomb as she was walking across the mud with her husband Bob at Dovercourt as the tide went out.
After hearing her shout, her family ran over and discovered two more of the hand grenades, which date back to the Second World War.
The 37-year-old of Milton Road, Corringham, said: “It was just unbelievable, I am still in shock."
Captain Nick Mathieson, of the Explosive Ordnance Disposal Regiment, said: "Blowing the grenades up in situ was the safest thing to do as old ammunition can be quite unstable.
“They were in very good condition and looked like they had been placed on the beach rather than washed up from the sea.
“I would encourage people to call 999 if they have concerns about any suspect items they find and not touch them. It is better to be safe than sorry."