Pictures show a Royal Navy Bomb Disposal vehicle and specialist officers at the scene.
A Royal Navy spokesman said: “On Sunday the Royal Navy’s Southern Diving Unit Two attended a site in Pagham, West Sussex to dispose of a suspected explosive ordnance.
“The site was successfully made safe.”
A Sussex Police spokesman said: “Military Ordnance Disposal attended a small World War II device which had been found at Pagham Harbour on Sunday morning and carried out a controlled explosion that afternoon. No evacuations were necessary.”