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What it’s like to dive in the New England Aquarium’s giant tank (watch out for Thomas the eel)

I’ve always wondered what it would be like to dive inside the Giant Ocean Tank. Finally I got to find out.

A look at what it’s like to dive in the New England Aquarium’s giant tank
Reporter David Abel has long wondered what it would be like to dive in the New England Aquarium's Giant Ocean Tank. He recently got the chance to find out. (Olivia Yarvis/Globe Staff)

Twenty-three feet below the water’s surface, coiled in a crevice of artificial coral, the bottom-dweller sensed my presence. He turned his emerald snout in my direction and started slithering toward me. A few feet from my face, the carnivorous creature opened his mouth wide enough that I could see his dagger-like teeth.

This was how I became acquainted recently with Thomas, a nearly 6-foot-long, 17-year-old moray eel, one of about 600 animals that live in the New England Aquarium’s Giant Ocean Tank. Thomas hadn’t eaten yet that afternoon. He kept swimming toward me — either thinking I might offer him food or serve as lunch.


“I was a little nervous,” Chris Bauernfeind, a biologist who looks after the tank’s animals, told me later.

Bauernfeind was my guide on a half-hour dive in the 4-story, 200,000-gallon exhibit at the heart of the aquarium, which opened in 1969. At the time it was the largest such tank in the world, so massive it had to be constructed first, and then the rest of the aquarium built around it. Now the replica Caribbean reef is a kind of magical marine microcosm, which includes loggerhead sea turtles, stingrays, hundreds of colorful reef fish, and a barracuda named Brodie.

Somehow predators and prey get along here, at least usually. A few times a month, one of the smaller fish among the 67 species here disappears. Thomas, Brodie, or some of the groupers can get peckish.

I’ve been diving for decades, since I was a senior in college and first experienced the otherworldly wonders of being underwater on an actual Caribbean reef. It felt like what I imagined it would be to trip on hallucinogenic drugs. I was mesmerized by the bright colors and unfathomably abundant life all around me; by the feeling of neutral buoyancy, which is as close to the feeling of flying like Superman as I expect to experience on earth; and by the spangled light shimmering through the water as the silvery bubbles from our scuba gear rose slowly to the surface.


Take a dive into the New England Aquarium
Reporter David Abel speaks about his experience diving into the four-story tank in the New England Aquarium.

On visits to the aquarium over the years, I’ve always wondered what it would be like to dive inside the Giant Ocean Tank — to be one of the few inside looking out, rather than among the million or so visitors a year on the outside looking in.

Thomas, the moray eel.Vanessa Kahn/New England Aquarium

I’m not the first to harbor that fantasy. Nine years ago an allegedly inebriated 51-year-old man from Quincy decided to take the plunge — sans permission — and swam around for a bit, before being arrested on charges of trespassing and disturbing the peace. (“Fortunately,” a spokesman for the district attorney said at the time, “the sharks had already been fed.”)

Of course, Bauernfeind and others on his team routinely descend into the filtered saltwater, which is pumped in from Boston Harbor, warmed to 74 degrees, and mostly replaced every 90 minutes. For several hours a day, the aquarists, as they’re called, do everything from hand-feeding some of the fish to performing a range of maintenance. That work includes cleaning the large acrylic windows — which range from about 2 to 3 inches thick — and maintaining equipment and vacuuming the waste that accumulates at the bottom of the tank. Then there’s the constant scrubbing of algae. “I wouldn’t call it the bane of my existence,” Bauernfeind says. “But it’s never-ending.”


There are other duties, which include fetching the many things that visitors regularly drop into the tank, such as cellphones, wallets, sunglasses, stuffed animals, and, at least once, a wedding ring. Divers also deliver the occasional marriage proposal by bringing down laminated, personalized signs that usually end with the big question: “Will you marry me?”

Another part of the job is guiding people like me through the underwater maze of faux reefs and aquatic life. Such tours used to be more common, but they have become rare since the pandemic.

My in was that I’m working on a documentary film that I thought might benefit from footage shot inside the tank. On a lark, I asked aquarium officials for permission, and to my surprise, they said yes. They sent over a form with guidelines that included bullet points such as: “Knives are prohibited.” And, later, release forms agreeing not to sue the aquarium in the event I became a predator’s lunch.

Thankfully, for me, there were no more sharks in the tank. A major renovation of the exhibit in 2013 cost $17.3 million and took 10 months to complete. It allowed the aquarium to increase the number of animals to about 2,000, including hundreds that divers had captured with hand nets on a trip off the Bahamas. But over the past decade, the population in the tank has decreased, given the short life spans of many fish and the vagaries of natural predation. Five sharks — three blacknoses and two bonnetheads — have died of natural causes and have yet to be replaced.


The writer (right) and his guide, Chris Bauernfeind, in the Giant Ocean Tank at the New England Aquarium.From David Abel

Bauernfeind said the aquarium was “going for a wow factor” after the renovation, but his team realized that a smaller population is more sustainable. The aquarium intends to replace the sharks, though it’s been difficult to do during the pandemic. That was OK with me.

On the afternoon of my dive, Bauernfeind briefed me on dos and don’ts. Unlike on a real reef, he said, I was free to stand on or touch any of the thousands of pieces of handmade, colorfully painted artificial coral. With his permission, I could also touch some of the animals, though — needless to say — it would be unwise to put my hands in their mouths. I should also be mindful, he cautioned, of looking up before ascending, given the large, lumbering sea turtles.

After suiting up and walking past a gaggle of curious visitors, I followed Bauernfeind through an opening in the glass barrier at the top of the tank to a ledge over the water. Before we could hop in, we had to wait for Myrtle, the aquarium’s famous 500-pound green sea turtle, to move out of the way. At nearly a century old, and a resident of the aquarium since it opened, she’s considered the tank’s grande dame.

After getting my bearings, we slowly descended into a kind of maelstrom of marine life, in which the fish and other creatures are constantly circling along the perimeter of the 40-foot-wide tank. Unlike in the wild, where animals tend to give divers a wide berth, the fish here didn’t seem to mind our presence. Many are so accustomed to people that I had to swim around them. At one point, I came face-to-face with Myrtle — inches from her sharp beak — and, with the OK from Bauernfeind, got to pat her on the back.


As we snaked through openings in the reef and around the large windows, I came to feel like I was part of the exhibit. Visitors on the outside waved to me, and I waved back. I wished I could deliver a marriage proposal.

Toward the end of the dive, as I descended toward a shadowy patch of coral at the bottom of the tank, I got my first glimpse of Thomas. His beady eyes at the top of his bright green head looked straight at me. I filmed him as he approached, and when I saw those sharp teeth, I ascended to get a bit of distance from him.

But Thomas kept coming.

Finally, Bauernfeind, who was keeping a close watch on our encounter, took the eel in his hands and moved him away from me.

Our air running low, and Thomas’s appetite running high, it felt like a good time to return to the surface.

More photos from the aquarium:

New England Aquarium visitors look out at the exhibits, including a section of the Giant Ocean Tank.Vanessa Kahn/New England Aquarium
A view of Myrtle in the Great Ocean Tank.Vanessa Kahn/New England Aquarium
A diver with a turtle in the New England Aquarium's Giant Ocean Tank.Vanessa Kahn/New England Aquarium
A cownose ray in the Giant Ocean Tank.Vanessa Kahn/New England Aquarium
A school of smallmouth grunts in the aquarium's giant tank.Vanessa Kahn/New England Aquarium

David Abel can be reached at Follow him @davabel.