The discovery raised to 22 the death toll from the tornado, which struck at 2 a.m. Sunday as people slept, making it the deadliest in Indiana in more than three decades. Vanderburgh County Sheriff Brad Ellsworth released no details about the latest victim, whose body was found within hours of work beginning to drain the 6-foot-deep pond.
Eighteen people died at Eastbrook Mobile Home Park, including four found Sunday in the pond, Chief Deputy Sheriff Eric Williams said.
"It is the one spot in this area that we have not thoroughly searched because it is under water," Williams said.
Ellsworth said the pond near the mobile home park would be drained by Monday evening to determine whether it held any other bodies.
Knight Township Fire Chief Dale Naylor said he believed that all survivors or bodies left in the wreckage had otherwise been found.
Four others, including a woman who was eight months pregnant, died from the tornado in neighboring Warrick County, east of Evansville. More than 100 people were taken to hospitals. Ellsworth said authorities did not have a count of any people missing because so many had left the area on their own.
Authorities were not yet allowing residents to return to check on their homes as crews continued to clean up and check that utilities had been shut off. National Guard troops were called in to help with search-and-recovery efforts.
"Mother Nature picked the worst place to drop in a tornado," Ellsworth said. "There's not a safe place to escape to. You're just up to fate at this point."
The youngest victim at the trailer park was a 2-year-old boy who was killed along with his 61-year-old grandmother, the Vanderburgh County coroner's office said.
The deaths in Warrick County included Cheryl Warren — a dental assistant who was eight months pregnant — her 4-year-old son, Isaac, and her husband, Jeremy, a truck driver. Authorities there also were counting as a fifth death the woman's fetus.
A loud roar was all the warning many residents got, reports CBS News correspondent Cynthia Bowers. Most were sound asleep when the sirens sounded early Sunday and, in truth, there likely was no place to hide from the fiercest tornado to hit Indiana in more than 30 years.
"It exploded, it just exploded, and other people's trailers were inside of ours," survivor Stacy Wright told CBS News. "We found kids inside our trailer buried under our stuff."
Mobile home park resident Tim Martin, 42, said he and his parents were awakened by the wind, which lifted their home and moved it halfway into the neighbor's yard.
They escaped unharmed, but he said they heard several neighbors calling for help. A neighboring mobile home was overturned, he said, and another appeared to have been destroyed.
"All I could see was debris," he said. "I thought it was a bad dream."
Indiana homeland security spokeswoman Pam Bright said the tornado was the deadliest in Indiana since April 3, 1974, when 47 people were killed. Those storms were part of one of the worst tornado outbreaks in U.S. history, which killed more than 300 in the South and Midwest and devastated Xenia, Ohio.
Ryan Presley, a meteorologist with the National Weather Service, said the tornado appears to have been an F3 on the Fujita scale, with winds ranging from 158 mph to 206 mph. The scale ranges from F0, the weakest, to F5, the strongest.