Queen Kaahumanu was said to visit Hanauma Bay during the early 1800s, while King Kamehameha V later described it as a favorite place to fish.

Today nearly 1 million people a year are drawn to the spectacular East Oahu bay, a coastal volcanic crater that has become the island’s premier snorkeling destination.

While Hanauma Bay was closed Tuesday as usual, it was opened to more than 60 workers, volunteers and politicians who gathered to celebrate the 50th anniversary of its designation as Hawaii’s first Marine Life Conservation District.

“There’s only one Hanauma Bay, the internationally acclaimed crown jewel of Oahu,” declared Lisa Bishop, president of the 200-member Friends of Hanauma Bay.

With a stunning bay sparkling behind them, speakers told the gathering about their memories of visiting the bay and thanked the volunteers and workers for helping to keep the area special.

A few politicians couldn’t make it but sent congratulations anyway. Among them was former President Barack Obama, who described Hanauma Bay in a letter as his refuge, especially when he was growing up on Oahu.

“A day at Hanauma Bay is always a day well spent,” wrote Obama, who always brought his daughters to the bay during his Christmas vacations in Hawaii. “And I’ve cherished all the days I’ve gotten to teach my own children her secrets over the years.”

The bay’s designation as a marine life district in October 1967 made it illegal to fish or remove any marine life or other marine resources from the bay.

State officials said the designation drove the state Department of Land and Natural Resources into an active role in managing and protecting the bay’s waters. State biologists have been surveying fish populations there since 1969.

Today the bay embraces nearly 450 species of fish and offers the largest mass of reef fish anywhere around Oahu.

Several people Tuesday reminisced about what happened 50 years ago. Chapman Lam said that when he heard about the state hearing about the proposed district, he felt compelled to show up. But he said he was appalled when only fisherman were speaking against it.

“That’s when I stood up and said we needed a conservation district,” he recalled.

Despite the opposition, the state Division of Fish and Game approved the marine district, and Lam — then leader of the Hawaii Council of Diving Clubs and a Navy lieutenant commander at Pearl Harbor — would end up organizing teams of divers who conducted volunteer surveys in the bay for a full year to determine exactly what kind of resources existed there.

It wasn’t long before Hanauma Bay’s popularity took off. Tourists were brought in by the busload, and as many as 10,000 people were snorkeling and feeding fish in the bay every day. By the late 1980s as many as 10,000 people were using the bay in a day, and there were more than 3 million visitors a year.

Visitors parked their rental cars on the lawn or on the highway, and commercial tours were dominating the picnic facilities. The situation was out of control, officials acknowledged.

“If there was a buck to be made at Hanauma Bay, someone was going to find a way to do it,” remembered Alan Hong, who became Hanauma Bay’s first manager under a new management plan created in 1990.

Under the plan, Hanauma Bay started restricting commercial operators, automobiles and the number of visitors.

By 1993 Hanauma became the first “no smoking” public beach in the nation and then started charging an admission fee in 1995. In 1997 Hanauma Bay won the international Tourism for Tomorrow award, the world’s top accolade in sustainable tourism, given out by the World Travel &Tourism Council. In 1999 the state banned fish-feeding in the bay.

Dick Baker, a former president of the Friends of Hanauma Bay, led a task force appointed by then-Mayor Jeremy Harris that eventually led to $13 million in improvements at Hanauma, including a visitor center that opened in 2002.

“We have a world-class educational and support facility for a world-class environmental and educational site,” Baker said after Tuesday’s ceremony. “I’m hugely satisfied and pleased with what came about.”

Bishop said Oahu is blessed to have Hanauma Bay and the restrictions that have prevented the 100-acre facility from being loved to death.

“If we did not have the designation 50 years ago, we would be completely fished out,” she said. “We would not have the coral reefs we would have now. All of the reefs would have been destroyed.”