The water-filled hole called Palm Sink in Hudson varies in depth from about 120 to 145 feet. At the bottom, it is cold and dark, and dissolved hydrogen sulfide makes the water smell like rotten eggs. Even with a light, visibility is only a few feet. These conditions complicated the task of divers from the Pasco County Sheriff's Office and other law enforcement agencies who were trying to raise two cars _ and possibly a body _ sighted in the sinkhole early Thursday morning.
In addition, divers had to contend with the dangers posed by nitrogen narcosis, a condition that limits the time divers may spend in deep water. After spending a few minutes at the bottom of Palm Sink, a diver might have to allow an hour or more for the ascent, to allow the body to release nitrogen absorbed into the tissues.
Palm Sink "is not an enjoyable place to visit," said Paul Heinerth of Hudson, a professional diver who raised a stolen Mercedes-Benz from the sinkhole with a crane about seven years ago.
The odor of rotten eggs, generated by rotting vegetation that has fallen into the sinkhole, is something you can "smell through your equipment, and taste," he said.
"There's so much trash _ newspaper boxes, beer cans, tires, you name it," said Heinerth. "That's why no one really dives there. . . . It's on the bottom of my list."
Heinerth, who owns the Scuba West dive store and school in Hudson, and who has accumulated 7,000 hours of diving time, said he has been in Palm Sink about six times.
"In that particular sinkhole, the visibility is not good," Heinerth said. Tannic acid in the water gives it the color of "iced tea," he said.
"If it's undisturbed, visibility may be 20 feet, if it's really good. Probably it's 3 to 5 feet visibility. Once you stir up the very fine silt that's laying on the bottom, you can't see anything."
Light from the surface penetrates no deeper than 40 feet, he said. The water is a combination of salt water and fresh water.
"There are no fish because of the consistency of the water," he said. "There's virtually no oxygen in it, nothing alive down there."
For safety, sheriff's officials said they were limiting divers' time on the bottom to about five minutes.
"You really don't have time but to go down, look around and come back," Heinerth said.
A diver might take a few minutes getting down, spend five minutes on the bottom, then take an hour or more making stops on the ascent to let his or her tissues release nitrogen; a few minutes at 40 feet, eight to 20 minutes at 30 feet, 20 to 30 minutes at 20 feet, then 40 minutes to an hour at 10 feet.
Heinerth said he didn't know much history of Palm Sink, but said, "It's been there since before white man was on these shores.
"I heard about it in 1971 and got a peek back then. I didn't get turned on."