The Tybee Bomb as described by Wikipedia:
The Tybee Bomb is a 7,200 pound Mark 15, Mod 0 hydrogen bomb that was lost in the waters off of Savannah, Georgia on February 5, 1958. The bomb was jettisoned during a practice exercise after a B-47 bomber carrying it collided in mid-air with an F-86 fighter plane. It is presumed lost somewhere in Wassaw Sound off the shores of Tybee Island. The bomb is one of eleven known missing nuclear weapons from the U.S. nuclear arsenal.
The NBC station in Savannah, GA is reporting:
The Air Force is coming to Savannah next week to investigate new information on the Tybee Bomb. The military is interested in claims a Statesboro man (Derek Duke, a retired Air Force colonel) found the 8-ton nuclear weapon lost in an accident in 1958.CNN added:
It’s believed to be in less than 20 feet of water somewhere in Wassaw sound between Wilmington Island, Little Tybee Island and Wassaw Island. [...]
[Lt. Col.]Smolinsky said if the bomb were found, a decision would have to be made about whether to try to recover it or leave it where it is.
An Air Force investigation concluded in 2001 that the bomb is probably harmless if left where it is. It also said a recovery operation could set off the conventional explosives in the bomb that would put the recovery crew at risk and do serious environmental damage.
The 7,600-pound, 12-foot-long thermonuclear bomb contained 400 pounds of high explosives as well as uranium.
The Air Force insists the bomb was being used for practice and did not contain the plutonium trigger needed for a nuclear explosion.
The accident took place the morning of February 5, 1958, over the coast of Georgia. [...]
Air Force Assessment of Reported Elevated Radiation Resulting from a 1958 B-47 Accident -- 44 page report [.pdf] dated May 31, 2005
The Air Force has reaffirmed that the lost incomplete bomb is the property of the United States Government, and has consistently asserted that the best course of action in this matter is to not continue to search for it and to leave the property in place. Due to the concerns previously expressed, the Air Force continues to reject any offer of salvage.
The Air Force considered the case to be closed until 2004, when media reports indicated a citizens group named ASSURE (American Sea Shore Underwater Recovery Expedition) had discovered enhanced levels of radiation and were concerned that the elevated readings were associated with the lost bomb. In response, the Air Force organized a team of experts to evaluate these reports, with representatives from several organizations. It was determined that the next step was to conduct a radiological survey of the area to ensure valid survey methods, equipment, and readings.
Using sodium iodide detectors, the Air Force-led team surveyed the Wassaw Sound area identified by ASSURE, detecting variations in radioactivity, although the magnitudes reported by the ASSURE team were greater. By utilizing high purity germanium detectors, the source of the radiation was identified as naturally occurring radioactivity. Specific emphasis was placed on determining the presence of the two isotopes of uranium that would indicate presence of the Mk15. These two uranium isotopes were not detected using gamma-ray spectral analysis.
A wide area survey was performed using an array of six sodium iodide detectors towed behind one of the team boats. This allowed a larger area to be covered during the radiation survey. The broad area survey results detected approximately the same radiation levels found by a second team boat, but no indication of the Mk15.
No new information was uncovered that would lead the Air Force to modify the conclusions reached in 2001. Valuable experience was gained in utilizing modern radiation detection methodology in this endeavor.
Lost nuclear bomb possibly found [CNN]
Group says it may have found missing H-bomb off Georgia's coast [First Coast News]
Air Force Takes New Look at Tybee Bomb [WSAV News 3]
Bomb Hunter [ABC News]