They pulled up their Minnesota trucks and boats Sunday morning to a hurricane-tattered intersection in eastern New Orleans, and a dozen deputies from the Ramsey County Sheriff’s Office took their first steps into the foul, green-gray water that has submerged much of this city for two weeks.

They didn’t know the area, didn’t know people here, but they knew their tall task at hand: Check on addresses where New Orleans authorities received 911 calls in the past few days, then go door to door looking for signs of life or death at every building in 40 square blocks.

The deputies — most of them members of the Ramsey County sheriff’s dive team — are part of a wide and painstaking effort to rescue those still stranded after two long weeks and recover the bodies of those who didn’t make it. They have volunteered to stay for as long as three weeks, sleeping in their own campers and eating food they packed back home.

Though the flooding has subsided some, many areas still require combinations of boats and high-water vehicles to search. Ramsey County deputies navigated their watercraft through downed wires, downed trees, flooded cars and submerged junk. One of their boats, an aluminum fishing craft, contained a depth-finder showing 12 feet of water at times, they said.

Deputies, who most often use the craft for water rescues on Minnesota lakes and the Mississippi River, described it as something they’d never seen the likes of.

“It’s devastation. It’s totally surreal,” said deputy Mike Thommes. “It looks like it just hit so quickly that no one had time to react.”

Cars were still parked neatly in the driveways in the neighborhood with post-war brick houses where the deputies patrolled. Dogs left behind swam in the muck, took refuge in trees or stayed on porches, withering away with no one to feed them.

The water’s edge was filled with remnants of life in the neighborhood: women’s shoes and flip-flops, a “Count of Monte Cristo” DVD, a family photo album, a baby’s rattle.

This mission also prompted the deputies to carry automatic weapons and wear bulletproof vests along with their hip waders. When they pulled their boats and trailers into one staging area, they heard gunshots.

“You can’t let your guard down,” deputy Tony Waldo said.

The water and the muck it leaves behind are slippery. It is so contaminated that they wash off boots with bleach and will end up throwing away some of the clothes they wore in it.

Lt. Ron Petrusson, who heads Ramsey County’s water patrol division, got a splash of the water on his face, he said, and immediately spread hand sanitizer on his skin. “It was gross,” he said.

And with temperatures in the 90s, it was only getting grosser.

The deputies spent much of the day yelling to empty houses,“Sheriff’s office! Rescue!” then listening in silence for a quiet response. They banged on windows but did not break into any of the dwellings — federal officials had told them not to.

In one office building, a homeless man holed up on the second floor asked them for drinking water and the deputies threw him a few of the bottles they had with them in the boat. The man refused to go with them, they said, saying he didn’t want to be part of their world anymore.

When they left empty houses, they spray-painted an X on each building and marked quadrants of the letter with the date, their office acronym, the number of hazards around the building and the number of living or dead people inside. On Sunday they marked mostly zeroes, the neighborhood so deserted they rescued only dogs.

“We came down because this is the kind of thing we do,” Petrusson said. “The amount of suffering that’s going on down here, it’s on a scale that’s never happened in the country before.”

Thommes said volunteering wasn’t a question for most of them. “How can we not?” he said. “We can’t just sit and watch.”