Koa spins slowly, gracefully in the water, only her sleek silvery-gray head visible as she uses her senses of smell and hearing to suss out her new surroundings. Her eyesight may be failing, but she seems calm and unafraid.

That might be because Koa and her longtime roommates, Ola, Nani, Paki and Opua, have a “Golden Girls” situation going on. The five female Hawaiian monk seals, all about 20 years old, have lucked out with some posh new retirement digs at the Minnesota Zoo.

Outside of the Hawaiian islands, the zoo is the only place that the public can view these rare seals.

One of the most endangered sea mammals in the world, the Hawaiian monk seal has been in steep decline since the 1950s and is a high-priority cause for the National Oceanic and Atmospheric Administration (NOAA), an arm of the U.S. Department of Commerce that oversees marine conservation. The NOAA estimates there are only about 1,000 left throughout the island chain.

While the primary goal is to rehabilitate and nurture these seals in the wild, their tendency to go blind puts them at risk. The Minnesota Zoo has arranged to house and care for “the girls” as part of its own conservation efforts. The new seal exhibit, featuring underwater viewing behind glass and chances to observe feeding and training, opens Saturday.

“These girls will stay with us and help tell the story of their counterparts in the wild,” said Melanie Oerter, a marine-mammal zoologist at the zoo who received a grant to visit a rehab facility for monk seals in Oahu.

Monk seals are called living fossils because of their unique lineage dating back 15 million years. One of only two surviving species — a Caribbean version went extinct in 2008 and a Mediterranean one is also endangered — the Hawaiian monk seal faces mounting threats to survival.

They are preyed on by sharks in the water and dogs or people on land. They get entangled in ocean debris such as stray fishing nets. They are vulnerable to disease because of a lack of antibodies. Habitat loss, including beach erosion and shrinking food supplies, have made their chances even worse.

“They love crustaceans like lobster and especially octopus,” Oerter said. “But the juveniles have trouble learning to hunt when there’s not enough food, and only one in five makes it to a reproductive age.”

The five seals at the Minnesota Zoo have lived together in rehab since 1995, but they are solitary by nature, Oerter said — hence the nickname “monk,” although that’s also attributed to their taupe neck folds, resembling a monk’s cowl or hood.

“They’re playful and curious, but they prefer their space.”

Unlike other seal species that are more widespread, Hawaiians are strictly tropical.

“They love to hump themselves up on some warm lava rock and bask,” she said.

And “hump” they must, owing to their large size and lack of dexterity on land. They can grow up to 500 pounds, and their short front flippers can’t propel them across the sand like more agile sea lions.

Hawaiian monk seals can live up to 30 years, and Oerter anticipates that the zoo could become home to more: “Most of our guests have probably not even heard of these seals before, and the first step toward saving them is making that connection.”