In 1924, Shedd Aquarium was presented as a gift to the city of Chicago from John Graves Shedd, president and chairman of the board of Marshall Field & Co.

But the more than 80-year-old museum also is a gift to the more than 2 million people, from countries all around the world, who visit the impressive facility every year.

The building, with an octagonal center that’s covered in white Georgian marble, has the standard aquarium displays, but you don’t just have to be a typical surface swimmer, er … visitor, at Shedd. Dive a bit deeper and you’ll find an exciting world full of creatures with fins, stingers, tentacles, feathers and beady eyes, plus learn what is needed to save populations of aquatic animals that are on the verge of extinction.

“Everyone seems to have a different connection to different exhibits,” said Kayley Ciocci, a Shedd Aquarium spokeswoman.

Visiting the aquarium is almost like taking a trip around the world … starting close to home with the Great Lakes, strolling over to the Caribbean, gliding along the Amazon and marching into the Polar Play Zone.

“In all, we have more than 32,000 animals — 1,500 species,” Ciocci said. “It is one of the largest and most diverse collections of aquatic animals in the world.”

The animals and fish arrive at the aquarium via various routes. Some are donations, others are brought here from other aquariums, a few are born on site and a lot of them are rescued from accidents or tragedies at sea.

“One story everybody loves is that of our sea turtle named Nickel. She was hit by a boat and her buoyancy is off from the accident, so she floats and swims perpendicular with her butt up in the air,” Ciocci said. “(Staff members) rescued and rehabilitated her, and now she lives here at Shedd.”

You know you are arriving at a special exhibit when the loudest things you hear are the squeals of excitement from the children. And at Shedd, that happens a lot.

It starts from the moment you walk into the exhibit space and you see the Caribbean Reef.

“There are 90,000 gallons of water in the Caribbean Reef tank,” Ciocci said. “There you can see stingrays, sharks, eels, a sea turtle and hundreds of fish of all colors.”

Divers, who are staff members or volunteers of the aquarium, make regular appearances in the Reef tank. They talk to the visitors, share information about the aquatic creatures inside or tend to the fish.

“The divers will come in several times a day to feed them. Certain ones will need special attention,” Ciocci said. “So like the sea turtle, she eats a lot, and sometimes she will get special food, like lettuce leaves, to kind of distract her while the other ones eat.”

In its lifetime, the aquarium has had two major additions to the main building. The Abbott Oceanarium, which covers 170,000 square feet, opened in 1991. It’s four levels and is built on 1.8 acres of lakefill, manmade greenspace that is cut into Lake Michigan. The Wild Reef exhibit opened in 2003. It has 26 interconnected habitats and more than 575,000 gallons of water. The Shedd imported 17.5 tons of sand from the Philippines to use as a seabed, a shark habitat and part of the exhibit floor in the Wild Reef.

The Oceanarium is home to the beluga whales, the Pacific white-sided dolphins, sea otters and sea lions. Guests can see live coral and sharks in the Wild Reef area.

But one of the most visited exhibits is the Polar Play Zone, home to the Magellanic and Rockhopper penguins.

“The penguins are very popular,” said Christine O’Connell, manager of communications and public relations at Shedd Aquarium. “Their habitat is about 65 degrees, and they are involved in the special Penguin Encounter. … They like to be touched. One of the trainers was telling us that the penguins actually seem to remember (the trainers).”

Interactive exhibits and opportunities are a special part of the aquarium. For an extra fee ($46.95-$350), people can touch the penguins, climb in the water with the beluga whales, experience a shark “feed” or be a trainer for a day. If you don’t want to spend the extra money, the Stingray Touch ($5 added to general admission) and the Sturgeon Touch allow you to connect with the fish and aquatic creatures.

“Certain animals, not used to human touch, would get too stressed out from being handled by humans,” Ciocci said. “But we did a study on our stingrays in the Stingray Touch, and they tended to be less stressed and more comfortable because they are used to being handled by humans. It doesn’t bother them anymore when we have to check on them, unlike other animals.”

The trainers, volunteers and staff at Shedd Aquarium certainly act as a family to the animals, fish and each other.

Some have degrees in marine biology, others have been at Shedd for a long time and many of the volunteers have been trained by experts on how to do their jobs. Shedd employs researchers who work in the Great Lakes with fresh-water fish or in the Amazon. While the researchers don’t work daily in the aquarium, they contribute to the overall mission of Shedd, which is to have the animals connect you to the living world, inspiring you to make a difference.

The staff members and volunteers are dedicated to the aquatic life and to conservation.

“We rescue a lot of our aquatic life,” O’Connell said. “We also have a dog program here with five rescue dogs, we have rescue birds — three different birds of prey, Nickel was obviously rescued and most of the otters are rescued.”

Feeding the population at Shedd is a chore in itself, but also is part of the facility’s conservation efforts. All of the aquatic life gets high-grade, sustainable seafood.

“We are very careful to make sure we are not depleting populations of fish that should not be depleted just to feed our fish and aquatic animals,” Ciocci said. “We have relationships with other aquariums in the Association of Zoos & Aquariums where we have the same goals of conservation and research, and we get together a lot to talk about those efforts.”

But the ultimate goal of Shedd Aquarium is to make sure you have fun while exploring a whole new world.

Maggie Hradecky: 815-987-1367; mhradecky@rrstar.com; @maggiehrad

If you go

On-site general admission*: $8, adults; $6, children; free, children ages 2 and younger.

For more information and pricing: 312-939-2438; sheddaquarium.org

*On-site general admission includes the Waters of the World, Caribbean Reef and Amazon Rising exhibits only.