In a county where any housing within close to a half-mile of a school is off-limits for sex offenders, five convicts have been forced to call the low space under the Julia Tuttle Causeway home.

Above their heads, the loud wooshing of cars headed to and from Miami Beach's warm sands and nightclubs. Below their pallets — if they have them — rats scurry. Add to that the fear that comes with being hated and vulnerable.

"You just pray to God every night, so if you fall asleep for a minute or two, you know, nothing happens to you," said 30-year-old Javier Diaz, who arrived this week. He was sentenced in 2005 to three years' probation for lewd and lascivious conduct involving a girl under 16.

Even some who consider this concrete makeshift shelter just deserts might reconsider if they looked around. About 100 feet away are Biscayne Bay's blue-green waters, where a family with young children played this week.

The conditions are a consequence of laws passed here and elsewhere around the country to bar sex offenders from living near schools, parks and other places children gather. Miami-Dade County's 2005 ordinance — adopted partly in reaction to the case of a convicted sex offender who raped a 9-year-old Florida girl and buried her alive — says sex offenders must live at least 2,500 feet from schools.

"They've often said that some of the laws will force people to live under a bridge," said Charles Onley, a research associate at the federally funded Center for Sex Offender Management. "This is probably the first story that I've seen that confirms that."

The five men under the causeway are the only known sex offenders authorized to live outdoors in Florida, said state Corrections Department spokeswoman Gretl Plessinger.

"This is not an ideal situation for anybody, but at this point we don't have any other options," she said. "We're still looking. The offenders are still actively searching for residences."

She conceded a point that many experts have made: This "is a problem that is going to have to be addressed. If we drive these offenders so far underground or we can't supervise them because they become so transient, it's not making us safer."

County Commissioner Jose Diaz said he had no qualms about the ordinance he created.

"My main concern is the victims, the children that are the innocent ones that these predators attack and ruin their lives," Diaz said. "No one really told them to do this crime."

The men must stay at the bridge between 10 p.m. and 6 a.m. because a parole officer checks on them nearly every night, Plessinger said.

Some of them sleep on cardboard raised slightly off the ground to avoid the rats. One beds down on a pallet with a blanket and pillow. Some have been there for several weeks.

"I mean, you really don't get a good sleep over here, but it's better than being in jail for right now," Javier Diaz said.

They have fishing poles to catch food, cook with small stoves, use battery-powered TVs and radios and keep their belongings in plastic bags. Javier Diaz has trouble charging the GPS tracking device he is required to wear; there are no power outlets nearby.

He said he and the other men fear for their lives, especially because of "crazy people who might try to come harm sex offenders."

The five committed such crimes as sexual battery, molestation, abuse and grand theft. Many of the offenses were against children. The state moved the men under the bridge from their previous home — a lot next to a center for sexually abused children and close to a day care center — after they were unable to find affordable housing that did not violate the sex-offender ordinance.

Twenty-two states and hundreds of municipalities have sex offender residency restrictions, according to a California Research Bureau report from last August.