While scuba diving for hammerhead sharks in a Cuban mangrove, Melissa Márquez felt a pair of teeth lock onto her leg.

The worst thing I thought would ever happen during a field excursion was losing an expensive piece of equipment. As a scientist specialising in the habitat use of chondrichthyans (sharks and their relatives), the thought of a shark swimming away with a few grand on its dorsal fin, never to be recovered again, was always in the back of my mind. On a recent special trip to Cuba, with no such equipment around or in my care, I thought I was in the clear for any bad luck field experiences. I was wrong.

Slipping into the warm Caribbean waters to film for Shark Week 2018, safety was our number one priority. We were diving in an area inhabited not only by sharks but also another fierce predator, the American crocodile. Found in the Neotropics, Crocodylus acutus is the most widespread of the four extant species of crocodiles from the Americas, but is considered threatened in nearly all parts of its range. Living for 70 years and reaching up to 4.5 metres and 900kg, they are a prehistoric creature that is endangered by habitat destruction and illegal hunting.

While night diving for hammerhead sharks, we ventured into a mangrove swamp, and came upon a three-metre crocodile. We were able to get some cool footage of it — you’ll hear a few moments in the show where I let out an expletive because of how close we did get (sorry, parents!). After some time, the crocodile disappeared into the murk and we decided to wrap up our day.

My dive mask had been acting up, so while underwater I relied on visual cues. My dive buddy signalled we were to ascend, and, not wanting to get hit by his fins, I stayed sitting on my knees on the sandy bottom. In the dwindling light, a sudden hard pressure overcame my left calf, and then I was dragged.

There was no pain. Given that we’d been diving with a crocodile, I quickly realised what exactly was biting me. As it slowly dragged me backwards, my hands splayed out to the sandy bottom to see if I could grab something to possibly hit it or pry my leg out. Nothing. Hoping the safety crew could hear me, I slammed down my microphone button and said, “I’ve been bit! I’m being dragged!”

I had never heard of anyone being bitten by a crocodile while scuba diving, so I drew on what I knew about these predators. I didn’t dare move my leg, or it could bite down harder and rip a chunk of out my calf — or worse, roll and take my leg with it. A large crocodile species, its snout has 14 to 15 conical teeth on each side of its powerful jaw and a bite force of 3,700 pounds per square inch (or 16,460 newtons).

Seconds ticked by, and the crocodile finally released my leg. Relief flooded my senses and I thought “Screw it!” to the safety stop. I filled my buoyancy control device with air and shot to the surface. Once there, I alerted my medic to what had just happened and was taken out of the water. When I finally saw my leg, I quickly realised it could have been worse.

I believe what I experienced was an exploratory bite. The only way many animals, like sharks and crocodiles, can explore an object or organism is to bite it and see if it is suitable prey. Not moving my leg and wearing a scuba suit (made of neoprene, a weird texture) probably helped the crocodile realise I wasn’t food. While ‘playing dead’ worked for me, experts do suggest running or fighting back if possible.

I won’t bore you with the “after” details — it includes lots of cleaning, a ton of antibiotics, and a jaunt at a Miami hospital — but I do want to emphasise I do not blame anyone (animal included) for what happened. As scientists who study predators, there is always a risk when working with them, and I’m fortunate I had a team that leapt into action to prioritise my safety. My advice? Remain calm, learn about the predators that call your field site home, and have medical supplies with you. It might just save your life.