A series of dives by researchers this summer off Maui’s southern coast has added a bit more knowledge of the graveyard of military wrecks that lies off Hawaii’s shores.

The National Oceanic and Atmospheric Administration and the University of Hawaii conducted a survey of World War II-era aircraft and amphibious tracked vehicles that had been discovered previously but not documented in detail, said Hans Van Tilburg, NOAA maritime heritage coordinator.

A survey team produced scale drawings and took photos of six wreck sites, including those of a carrier-based SB2C-1C Helldiver dive bomber, a carrier-based F6F Hellcat fighter and three amphibious assault vehicles.

Prior to major invasions in the Pacific, Marines and Army soldiers trained in landing craft and assault vehicles along Maui’s southern coast from Maalaea Harbor to Ahihi Bay, NOAA said.

One of the amphibious vehicles was an open-topped LVT-4 cargo carrier, and the other two were armored LVT-A4s with gun turrets and 75 mm howitzers.

“So there may be a story there about the loss of these (amphibious vehicles) during training,” Van Tilburg said. “But the problem with investigating these topics is it’s difficult because during wartime there was censorship, so there’s not a story that may have been sent around at that time.”

A lot of military hardware and ordnance was simply dumped offshore after World War II, but Van Tilburg doesn’t believe that was the case with the amphibious vehicles, which were surveyed in 60 to 80 feet of water.

“I checked with the state, and the files with the (Department of Land and Natural Resources) don’t have any record of putting these down as artificial reefs or anything, and looking at the wreck sites themselves of these amphibious vehicles and the kinds of things that were on them, they don’t appear to be intentionally sunk,” Van Tilburg said.

The identity of the F6F Hellcat is another mystery, NOAA said.

Van Tilburg said the dives were part of an ongoing project to collaborate with the UH Marine Option Program to train UH science divers in survey techniques for historic sites.

There is no doubt many are out there.

A report compiled by UH for the Naval Historical Center found about 80 sunken Navy ships and submarines and more than 1,400 naval aircraft lost in Hawaii waters, Van Tilburg said.

“Many of those could be in deep water, miles away, and some could be in shallow water and broken up,” he said.

The sinkings include that of the submarine S-28, a 219-foot S-class vessel that got underway from Pearl Harbor on July 3, 1944.

The S-28 acted as a target for anti-submarine warfare ships and made two practice torpedo approaches on a Coast Guard cutter, according to the Navy.

The Coast Guard cutter lost contact with the S-28, and no distress signals or explosions were heard.

A court of inquiry found that the S-28 sank on July 4, 1944, in 8,400 feet of water from a loss of depth control caused by “either a material casualty or an operating error of personnel, or both.”

In 2002, in a military debris field off Pearl Harbor, UH’s Hawaii Undersea Research Laboratory found the 78-foot Japanese midget submarine that was the first vessel sunk in the Dec. 7, 1941, attack.

In 2005 the lab also found the 400-foot wreck of the Japanese submarine I-401, the largest type of diesel electric submarine ever built. The subs were capable of carrying three folding-wing airplanes that would launch from a deck ramp.

The submarine was brought to Pearl Harbor after World War II and was sunk in target practice in 1946 off Barbers Point.