Another body has been discovered at Lake Mead near Las Vegas as droughts forced water levels to a record-low.
National Park officials did not say how long they think the corpse was submerged in the Boulder Beach area before being found on Monday.
It is the third body to be found since May in the mud due to water quickly receding due to climate change.
Clark County Coroner Melanie Rouse said it was partially encased in mud at the water line of the swimming area along the shore north of Hemenway Harbour marina.
The gender of the dead person was not immediately apparent and it was too early to tell a time, cause and manner of death.
Investigators are now reviewing missing persons records as part of the effort to identify the body.
The lake surface has dropped more than 170 feet since the reservoir was full in 1983.
It is now about 30% full.
The coroner said her office was continuing work to identify a man whose body was found on May 1 in a rusted barrel in the Hemenway Harbour area, and another man whose bones were found on May 7 in a newly surfaced sand bar near Callville Bay.
On July 6, the body of a 22-year-old Boulder City woman was found in the water near where she disappeared while riding a personal watercraft.
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Rouse said it may take several weeks to determine her cause of death.
The case of the body in the barrel was being investigated as a homicide after police said the man had been shot and his clothing dated to the mid-1970s to early 1980s.
The discoveries have prompted speculation about long-unsolved missing person and murder cases dating back decades — to organised crime and the early days of Las Vegas, which is just a 30-minute drive from the lake.
The drop in the lake level comes while a vast majority of peer-reviewed science says the world is warming, mainly because of rising levels of carbon dioxide and other greenhouse gases in the atmosphere.
Scientists say the west of the US, including the Colorado River basin, has become warmer and drier in the past 30 years.