Crawling with crabs

As each porcelain crab tried to wedge one of it's six sharp legs into the corners of my mouth, around my regulator, and under the silicon skirt of my dive mask, it occurred to me this may be the moment most people would question their career choice! But as more and more crabs enthusiastically used my face to find a foothold, my only thought was…

THIS IS FANTASTIC!

In January 2024 as part of a shoot for Blue Planet III, cinematographers Bérénice Mathieu and Santiago Cabral along with myself and Seasonal Seas Producer Jo Haley were completely surrounded by millions of porcelain crabs (more commonly referred to as 'changai' by the local Chileans).

The changai carpeted the boulders beneath us, packed in so densely that they piled upon one another several crabs deep. In the swell, every crab was fighting for a secure foothold, they gripped onto everything, including us.

Any surface became a foothold – our hoods and drysuits, the Velcro strap on our SCUBA tanks, even the camera housing itself. Their legs clung desperately to whatever they could find whilst their delicate limbs stretched out into the current, filtering plankton from the water. Letting go would mean being swept away.

As assistant producer and dive supervisor, I spent around seven weeks on location off the coast of Chile, alternating between topside filming of a sea lion colony located several hours away and filming the changai aggregation, timing our dives around underwater visibility.

Most of the time the water was an almost opaque shade of green - a sign of extremely high biological productivity. This is thanks to the influence of the Humboldt Current, an upwelling that brings nutrient-rich waters up from the depths and, in doing so, supports one of the most productive marine ecosystems on the planet.

Here, more than 1,000 crabs occupy every square metre of seabed, a unique combination of factors fuelling their extraordinary numbers. Plankton-rich waters provide an abundant food supply, while climate change has left oxygen levels too low for many other marine species to survive. Fishing pressure has also removed many of the changai's natural predators. The result – a population explosion of more than 200 million crabs.

Unlike many wildlife shoots, we didn't have to search for our animals. There was no waiting for them to appear, inching closer bit by bit, or spending hours waiting to see the behaviour we had come to film. The crabs were everywhere.

Instead, we faced a very different set of challenges.

The water was cold, really cold. Even in drysuits, thick hoods and dry gloves, our fingers soon became numb.

The surge was relentless. Filming with macro lenses and diving on rebreathers, it was like trying to focus on a target that was constantly moving. As the swell intensified, keeping a steady shot became almost impossible.

It was time to pivot!

We swapped out our rebreathers (a system that recycles the air we breathe, meaning no bubbles and longer dive times) for a nimbler open-circuit SCUBA set up. We loaded our tripods with as much weight as we could carry underwater, hoping to give ourselves at least a fighting chance of keeping the camera steady.

After weeks on location and countless hours underwater, I was really beginning to feel the fatigue. Even the crabs appeared to be feeling it – barely moving all day. Then suddenly, I caught a flash of silver out of the corner of my eye.

Baitfish.

Following them came the cormorants, diving between our legs and weaving around the cameras, looking straight at us with inquisitive eyes as they snatched individual fish from the shoal.

Then came the sea lions.

Four or five massive adults circled us in the pursuit of lunch. I hadn't moved an inch but for a few minutes, I found myself in the middle of a feeding frenzy.

I had never experienced anything like it underwater. And to top it off, the changai began to filter feed in perfect unison. As if sensing the moment we needed it most – nature suddenly put on an extraordinary show.

As they fed, the crabs formed remarkably well-organised lines across the face of the boulders. Their delicate net-like limbs reaching out into the current, moving as one.

When we returned to Bristol, we spent months trying to find someone who could explain what we had witnessed. Why were they organising like this? Yet the more experts we reached out to, the more remarkable a phenomenon it became.

Nobody really knew.

That was perhaps the most extraordinary thing about the entire shoot for me. We had spent a long time filming these animals, but in the end, there was still something happening here that science couldn't fully explain. I found myself thinking that sometimes the most amazing discoveries end up being the ones that leave you with more questions than answers.

It's not often in natural history filmmaking that you are lucky enough to witness something that remains a mystery to science. Rarer still is the chance to become so completely immersed in the environment you are filming.

On this sequence, we experienced both.

Witnessing the changai taking full advantage of the region's incredible productivity was a spectacular sight, yet it also felt like a glimpse into an ecosystem out of balance.

Changes in ocean conditions, fishing pressure, and other human impacts are allowing these remarkable aggregations to thrive. As extraordinary as it was – it was impossible to ignore the question of what this spectacle might be telling us about the future of our oceans in years to come.

In July 2025, a porcelain crab pick-up shoot was launched and local Chilean cinematographer Diego Bravo was able to join to help capture the last remaining shots for the changai sequence. Uruguayan cinematographer Santiago Cabral acted as Diego's mentor, coaching and supporting his development in using and filming with highly technical underwater filming kit – an opportunity made possible thanks to Project Songbird sponsored by Save our Seas Foundation.

Quote from Diego Bravo on location, aspiring cinematographer and Project Songbird candidate – "This is my first time working with professional equipment. I'm learning a lot, how to assemble the gear, how to use the cameras and also how to capture the moments under the water to tell these powerful stories. This is the first step to break into the natural history world"

Quote from Santiago Cabral reflecting on the shoot, cinematographer and mentor – "It was great having the opportunity to mentor a fellow South American, especially an aspiring underwater camera operator. This is exactly the opportunity I wish I had early on in my career. Diego showed great diving and camera skills as well as knowledge of the ecosystem. This kind of opportunity is priceless!"