There is today, in the waters of the Gulf of Mexico, a young male nurse shark that may answer to the name of Rohan. He is named for a boy from California whose mother recently leaped off a catamaran to check on a marine biologist who ... well, let’s back up a bit.

Rohan Ramanathan’s mother is Dr Latha Palaniappan. Their family, along with two friends, recently vacationed for a week on a catamaran out of Key West, Florida. Captain Corky and his wife Sue operate these excursions for small groups, snorkelling and birdwatching and generally nosing around the tiny islands that trail west off the tail of Florida’s keys. And for most of the week, they were beyond cellphone reach.

If it sounds idyllic, accounts the vacationers later sent only underlined that: clear waters, lazy days, spectacular fish for the snorkelers, sunset drinks and Sue’s fabulous meals on board.

Just over 100 km west of Key West is the Dry Tortugas National Park, a sprinkling of sandy islands that barely rise above the waves – some have even disappeared and reappeared over and over again. The largest is home to the enormous American Civil War-era Fort Jefferson. It was later used as a prison. Famously, one of the conspirators in the assassination of Abraham Lincoln, Samuel Mudd, was incarcerated here.

No prisoners these days, just occasional campers from the mainland who have to carry food and water along with their gear, or occasional catamaran-types who anchor offshore for a day or two.

Rohan Palaniappan and Captain Corky.

Latha Palaniappan and Rohan Ramanathan and company spent a sunny day exploring the fort and walking the beach. That evening, sated and happy, they sat in the catamaran, nursing drinks, chatting and planning the rest of the vacation. Sue was in the kitchen, pulling together another splendid dinner.

Out of the blue, a boat pulled up alongside. A voice called through the dusk: “Is there a doctor on board?”

That there was. Latha Palaniappan is an internist and medical researcher and among many other things, spent a year working with Médecins Sans Frontières in East Timor. She vaulted over the side and onto the other boat. They turned and sped to the Tortugan shore.

There on the beach, when Palaniappan disembarked, was a tall man. His name was Wes Pratt and he was a marine biologist. He and several colleagues spend weeks at a time on these islands, studying sharks. Though right then, sharks were very far indeed from their minds, for the tall Pratt was lying on the sand in a faint.

He had been out in a kayak all day, and the fierce Gulf sun had got to him. No surprise: in the long afternoons at this time of year, a thermometer in the Dry Tortugas can rise to 32 Celsius. A full day of that could knock anyone out.

Also present was a nurse, the mother in a family of campers on the island. Palaniappan was grateful for the help. They checked Pratt’s pulse (high) and blood pressure (low), then revived him and got him upright. Pratt threw up. Palaniappan said that at this point she realised she would need some details from him about his medical history and habits, and that this should be done in private. So she and the nurse shooed away the others and spent a quiet half-hour or so with Pratt.

They decided that he wouldn’t need a medevac – a helicopter from Key West or Miami – but he certainly needed a better diet than the protein bars and water he seemed to have been subsisting on. Fresh fruit and vegetables, for sure.

‘Don’t punch them’

Promising to check back the next day, Palaniappan left Pratt to rest and returned to the catamaran. Her son and the others were fascinated by her story. Captain Corky was particularly excited – he said he had never met a biologist. The next morning, they all returned to the island, bringing with them some of their fruit and veggies. Latha Palaniappan was encouraged to find Pratt was substantially better.

While she spoke with him in private, Pratt’s colleagues talked to the other people from the catamaran about their research. Rohan Ramanathan was captivated. All he knew about sharks before this day was, “you should not punch them if they attack you.”

But now these researchers had plenty to say about the animals’ natural behaviour, how they act around each other, their eating habits and much more. They tag certain individual sharks to get an idea of their movements and migration patterns. Ramanathan wanted to know how they tag a shark – simple, the tag is attached to its dorsal fin.

“It’s just cartilage,” he realised, “so it’s like piercing your ear.” Once that’s done, the shark sends the scientists location data for about 90 days, after which the tag detaches itself and floats to the surface.

Fort Jefferson in the Dry Tortugas in Florida.

Latha Palaniappan and Pratt joined them. She was satisfied that he was recovering well. He disappeared into the living quarters and emergeed with a book that features their work: Shark, by Brian Skerry. He scribbled a dedication: “For Rohan, with my thanks for your interest in sharks and for having an AWESOME MOM!”

Ramanathan was over the moon. Through the rest of their days on the catamaran, he saw sharks everywhere: “a small one that swam under the boat”, “a 7-footer near a shipwreck at the Marquesas Keys”, some that were “hiding in the mangroves” there, and “a really fast one” somewhere he can’t remember.

Still later, Pratt, now fully recovered and back to his beloved sharks, wrote Latha a note. “Today we caught and tagged our 15th shark,” he said, “a younger male [that we] named ‘Rohan’ this morning, hoping to inspire your son.”

Her son was certainly inspired. From that one nugget about not punching them, he now knows also that they are not scared of humans, and not even dangerous to humans. In his precious new book, he read: “Shark’s lives are full of so much more nuance and wonder than many people realise; they’re intelligent animals with rich lives – not just predators to be feared.”

Which may be why this 12 year-old said: “If you are gentle with them, they’ll be gentle with you.”

Dilip D’Souza is a writer who lives in Mumbai. He was most recently the co-author with Joy Ma of The Deoliwallahs: The True Story of the 1962 Chinese-Indian Internment.