National Aquarium visitors are encouraged to reach in to touch moon jellies in the Baltimore facility’s “Living Seashore” exhibit. (National Aquarium)

Two words you won’t hear when the National Aquarium opens its “Living Seashore” exhibit Tuesday: Don’t touch!

That’s because the new display features two saltwater pools filled with dozens of stingrays, skates, sea stars and other marine creatures just waiting for you to dip your fingers in and rub their backs.

For some visitors, this may require mustering a bit of courage. Horseshoe crabs, after all, don’t look very cuddly. And the 50 or so moon jellies pulsing around their low-lit pool are fascinating to look at, but — let’s be honest — a little creepy, too. They may be brainless blobs, but they can sting. Oh, don’t worry, you won’t feel it if they do, a helpful museum guide says. So go ahead, stick your arm in and stroke their little mushroom-shaped tops.

Spoiler alert: They feel like Jell-O. . . . And the skates feel like velvet. . . . And the moon snail feels like a croquet ball sitting in a puddle of pudding.

“Living Seashore” is the Baltimore aquarium’s first permanent “touchpool” exhibit in 17 years. It focuses on the Mid-Atlantic beaches that many of us visit each summer.

These moon jellies at the National Aquarium in Baltimore might sting, but you won’t feel it if you do. (Kate Rowe)

“But when you’re sitting on the beach, you have no idea what’s going on in the sand and offshore, day and night,” says Jack Cover, who oversees the aquarium’s exhibits. “We want to make families detectives,” to discover what’s there. “Beaches are a mosaic of different ecozones [and] they’re basically getting rearranged every day.”

“Living Seashore” begins at a sand dune pocked with holes made by ghost crabs. “They’re busy guys,” Cover says, “out mostly at night.”

Next, a slice of beach has been turned on its end to show the wrack line — that area where seaweed, shells and litter collect. Fans of “Where’s Waldo?” will have fun searching for the whelk egg cases in the wrack line and trying to guess why some shells have tiny holes.

In the offshore part of the exhibit, a large tank filled with manmade coral holds even more marine life. A striped burrfish, which looks like an underwater porcupine, swims by. Two dots in the sand are all you can see of a seven-inch northern flounder, which is keeping an eye out for food or predators.

Before the creatures meet the public, they get a health checkup. Museum staff members have spent months helping those in the touchpools get comfortable around people. Food is rationed because “it’s really easy to overfeed these guys,” Cover says. “They’re like your dog. They look like they’re constantly starving.”

They’re not. So go ahead, dip your finger in the water.

How you can help

Trash is a big problem at the beach. It’s unsightly for people and dangerous for animals. Discarded fishing line could wrap around a sea turtle’s flipper, leading to a deadly infection. That plastic grocery bag swishing around in the water looks a lot like lunch to animals that eat jellyfish.

What can you do? When you go to the beach, use the trash barrels. And take a trash bag and pick up what shouldn’t be there. “You’ll really be helping out,” says aquarium curator Jack Cover.

If you go

What: National Aquarium.

Where: 501 East Pratt Street, Baltimore.

When: Open daily at 9 a.m. Closing times vary.

How much: $21.95 for ages 3 to 11, $34.95 for ages 12 to 64, discounts for seniors and military. Admission is half-price on Friday nights.

For more information: A parent can go to www.aqua.org or call 410-576-3800.

— Marylou Tousignant