Joe Carter said he saw something floating in the water that appeared to be a charcoal briquette while he was boating Sunday with his father, the San Francisco Chronicle reported Thursday.

However, when the boy took the item out of the water, he discovered it was a Macy's jewelry box containing a diamond ring -- complete with price tag.

"Romance Princess. One-quarter carat. Diamond Wedding Ring. $499," the tag said.

Carter and his family said they took out a lost-and-found ad on an Internet bulletin board for the ring, which experts said is actually worth closer to $150, but no one has yet come forward to claim the item.

"I think it would be pretty sad to be someone reaching into your pocket for a diamond ring and find out it's not there," the boy said. "I hope I can find whoever that person is. That would be great."