Looking back, I see that jellyfish came to me when the haze of sleepless nights brought on by kids’ cries and the frenzy of cramming a working day into the scant hours of pre-school began to lift. And, even though I still looked good on Facebook, when I slowed down long enough to think, I felt lost and unfulfilled. That something inside had been waiting for the opportunity to climb out and look for more than flapjacks and yogurt wasn’t so surprising. That it was jellyfish certainly was.

As an ocean scientist-turned-science writer, I was working on a piece for National Geographic about ocean acidification, sometimes called global warming’s evil twin. This happens when carbon dioxide from burning fossil fuels mixes with water, making it more acidic, and harder to build shells in. And lots of marine creatures build shells. This story included a quintessential National Geographic graphic called “Winners and Losers”. On the losers’ side were shelled animals: coral, crabs, starfish. That made sense. On the winners’ side were shell-less things: algae, sponges and jellyfish. Jellyfish? What was their protection against acidic surroundings?

Delving into the scientific literature, I found only meagre evidence that jellyfish would be winners in future acidified seas. But as I delved deeper, I found stories about places where jellyfish were on the rise as a result of other human-induced problems: overfishing, pollution, coastal development and perhaps even climate change. Jellyfish seemed to navigate polluted waters better than other creatures.

In 1963, overfishing was rampant off the Namibian coast, one of the world’s most productive fisheries. Today, jellyfish dominate the ecosystem and sea lions are starving for lack of fish. In Japan giant jellyfish, which grow to a massive 220kg, appeared only three times during the 20th century. They’ve appeared every year of the 21st, probably as a result of overfishing, pollution and warming. The Mediterranean’s largest lagoon, Mar Menor, suffers from massive agricultural pollution. The jellyfish grew so thick in 2002 that you couldn’t drive a boat through the water. Near Israel, jellyfish that invaded from the Indian Ocean blanket the coastline for dozens of kilometres each summer. The swarms chase swimmers from the beach and gum up the cooling systems of power plants, forcing shutdowns.

Were these places indicators of larger global trends? Or were they just dramatic snapshots of natural cycles? Finding hard answers is complicated because jellyfish were systematically understudied by science for most of the 20th century. The way scientists studied the ocean was by driving motorised vessels that dragged huge nets; when they were reeled in with their mechanised winches, delicate gelatinous tissue was shredded in the process. On deck, scientists sometimes poured bleach over the nets to disarm jellyfish stingers before sorting their catch. Marine biology became biased towards durable animals that could withstand the rough treatment. So the history of jellyfish literally slipped through our nets, lost to us forever.

Soon after I discovered them, I moved into something of an obsession with gelatinous creatures. I set a Google alert on the keyword “jellyfish” for 2.25 each afternoon to devour jellyfish gossip before my kids arrived home from school. Most of the news stories claimed we should prepare for a jellymageddon – one of my favourite headlines was “Meet Your New Jellyfish Overlords.”

But the scientific literature was more cautious. In those articles, which I consumed like ambrosia, I became enraptured with just how extraordinary jellyfish are. Jellyfish make sense of the world with tiny faces dotted around the edge of their bells, complete with jellyfish versions of eyes, noses and ears. Their stinging cells fire with the fastest motion in nature. And jellyfish really are jelly-filled. They have a watery centre that allows them to swim with very little energy. It holds oxygen like a scuba tank so they can survive polluted water. The very spinelessness of the jellyfish is at the heart of their success.

Eventually, I figured I’d mastered enough jellyfish science to interview Jenny Purcell, one of the field’s most knowledgeable experts. When we spoke by Skype, I spent most of the call focused on the fantastic jellyfish facts that had so entranced me: their faces, their swimming, their stingers, their food. Finally, I got around to asking: “Do you think human activities or natural cycles are driving recent jellyfish blooms?”

She sighed deeply, as if I had finally asked a question that mattered. “One of the things I learned early on in my scientific career is that people often want an answer – one answer. It’s very complicated… There are climate drivers and there are human drivers. ” And then she trained her eyes on me and said something that stayed with me for all the years I’ve been chasing jellyfish: “And if you dare, that kind of story is a real story.”

Those words hit me like a charge, an intention. The real story of jellyfish isn’t limited to their unusual biology. Jellyfish are a harbinger of the most important issues facing us today: the health of the oceans, which is in turn the health of our planet and ultimately our own legacy on earth. If I were going to tell that kind of jellyfish story, I’d have to stop hiding behind my own insecurities as a scientist and as a writer. I’d have to grow a backbone.

It took a while. About a year later, I woke up in the middle of the night, startled by a rather strange thought: I had become a mid-40s suburban Texas mum with an obsession with jellyfish. How the hell had that happened?

I grabbed my iPad and wrote a list of important scenes in my life that had led me to that moment. I listed signing up for my first marine biology course and resolving to study maths at college, despite being told women shouldn’t study maths; how I worked for a cruel boss in a marine ecology lab; how I failed miserably at being an accountant. Moments in grad school, when cockroaches roamed my apartment and rats fell from ceiling tiles. I wrote about being with the wrong guy and not recognising it. About meeting my husband and not recognising it. About soul-sucking days as a postdoc.

When I scanned the list, I noticed a trend. Nearly everything on it was among the lowest points in my life. I was staring at an inventory of bad times. The troughs of my waves. Times when I was lost and unable to make sense of the world.

And then I saw that these low points were actually turning-points. They were the moments that pushed me to make a change. To break up with a destructive boyfriend. To change my career. To move from a toxic city. The low points – not the moments of joy – were the decisive ones. I had almost never made a change when things were going well. I had to feel bad to fix my life.

As the sleepless hours clicked by, I had a moment of clarity: I realised this idea of what drives change in us extended beyond my own life and into the larger world. To many of us lucky enough to live in developed countries, the threats to our oceans don’t seem that dire day-to-day. Our seafood counters are loaded with fish and shellfish. Visits to beaches don’t usually end with stings. The water doesn’t, on the whole, make us sick.

That’s not always the case, of course. Intermittently we have been receiving warnings. More intense hurricanes and more frequent floods remind us that things are not as they should be. But most of the time, many of us on the industrialised side of the planet feel comfortable. Our world is still functional.

So, why isn’t protecting our life-sustaining ocean more urgent? We haven’t yet reached the low point. Intellectually, we know we have problems, but we don’t feel them intensely enough. And so we figuratively pour bleach on the evidence. We ignore the ocean.

Disconcerting as this realisation was, a pinprick of light shined through my epiphany’s darkest corner. What was at risk wasn’t a boyfriend, a job or a move. It was so much more: our oceans, our health, our planet. I hoped we could change course before the waves took us under. But such a change would require willingness. It would require co-operative intention and effort. It would mean collectively growing a spine.

That’s where I came in. No more spineless, self-sabotaging fear. I needed to take action, to set my own course on my jellyfish odyssey, and then to share my voice with the world. Jellyfish – misunderstood, maligned, resilient, and of course, gloriously spineless – gave me the backbone to do just that.