A body was discovered in Glorietta Bay in Coronado Monday evening, Harbor Police confirmed.
According to police, the body was badly decomposed when it was found on a sandbar surrounded by water.
The San Diego Police helicopter made the discovery while flying over the bay. But it took a few hours before authorities could confirm that it was a body.
"They saw what they thought may have been a body," said Harbor Police Lt. James Jordan. "And we didn't know until hours later that it was a body."
Jordon told NBC 7, the water was too shallow for police boats to get close to the body so divers were called out.
At this time, it's unknown if it is a man or a woman, Jordan added.
"It's a mystery at this point how this person wound up there," Lt. Jordan said. "But we're confident the coroner will be able to determine what happened to this person."
The Medical Examiner's Office is investigating the cause of death.
No other information was available.