Petty Officer Jon Moore stumbled upon the clear glass bottle Thursday during a beach cleanup at the Pacific Missile Range Facility on Kauai.
Inside, he found a note from Saki Arikawa, four origami flowers, and a photo of Saki's sixth grade class in Kagoshima.
The note was dated March 25, 2006. It read, "I wrote this letter because we'll graduate elementary school so I wanted it to be a graduation memory."
Akira Nakashima, the principal of Kokubu Elementary School in Kagoshima, confirmed that Saki graduated from the school five years ago and that her class tossed the bottle from a nearby bay marking the event.
"It's just amazing that the bottle was found. I'm so delighted by the heartwarming news," Nakashima told The Associated Press.
He said that he is trying to locate the girl and the teacher to share the news.
The Navy says Moore was among 40 base personnel and 16 students and faculty from a Kauai school who picked up beach trash in observance of International Coastal Cleanup Day.