The sea is vitally important to our health and wellbeing, yet human activities beneath the waves wreak appalling damage, each day, across the globe. As we enter the second half of the United Nations Ocean Decade, an international effort to restore humanity’s relationship with the sea, Dr Cathy Cole reflects on the value of our ocean and the challenge of engaging with a world that is hidden from view.

It pulls me, madly, with its salt scent, the rush and scrape of shingle, the teasing winds that whip my hair, and the shocking assault of cold against my skin. Swallowed whole and tossed like a toy boat, I feel its power, its will, and in the first seconds that take my breath away, I am infinitely small, refreshingly insignificant. The charge of daily life ebbs instantly into the muted rhythm of the swell and I am held. Carried with the incoming tide, we pass Castle Point and swim with determined strokes towards the northern headland, glinting rose-gold with the first morning light. Below the froth that separates air from water, I can’t see more than half a metre, and the sun’s weak rays vanish quickly into ink.

After the swim, as I drip onto the rounded stones, my imagination fires with the hidden worlds playing out beneath the slick surface. In the shallows, when the water is clear, I’ve seen spider crabs lunging over barnaclecrusted rocks, shoals of fleeting silver darts as bream twist through sugar kelp and bladder wrack, cushion stars and crimson beadlet anemones, all awaiting the turning tide. In deeper waters, barrel jellyfish, pulsing ghostly white, sometimes as big as me, disappear as quickly as they emerge. We share the bay with bottlenose dolphins, year-round residents, but more easily seen in the summer when they roll and play in the surf. Just once, I shared a quiet moment of awe with a grey seal as we watched the full-moon set into the hazy dawn horizon.

Studying the state of our seas

I am deeply privileged to witness these glimpses into our marine world, and to have studied the seas throughout my career. As a Master’s student in Southampton, I feasted my senses on everything from the mathematics of the tides to the chemistry of ocean carbon to the secret records of summers at sea etched into salmon scales. Staying for a PhD, and with a strengthening stomach for high latitude seas, I was invited to join a research expedition in the Arctic Ocean to map and measure the bubbles of methane gas venting from sediments offshore Svalbard. This was a stark awakening to the potentially catastrophic nature of our changing climate, as warming temperatures on the sea floor threatened to destabilise reservoirs of methane hydrates and trigger “runaway” climate change. I started to tune in deeply to the changes underway in the seas, as they sequestered enormous quantities of heat and carbon.

A little more than a decade on, and my two-year old daughter has taken to yelling “I love you seeeea” daily as we fly towards it, perched on my bike down Penglais Hill in Aberystwyth. It stretches away from us, a tantalising canvas of greys and blues, depending on the weather. My son, who is five, tells me excitedly that he can’t wait to see tropical coral reefs and snorkel with turtles when he’s older. My stomach lurches, sick with grief. He does not know that, all around the world, marine heatwaves are relentlessly expelling the symbiotic algae that reefs rely on for healthy growth, exposing the vulnerable skeleton. For the first time, we have breached a climate tipping point, and we are seeing this catastrophic loss before our eyes. I don’t think he will ever see a coral reef.

The ocean’s vital role

Nearly three quarters of our planet is covered by sea. Always moving, it is vital to our climate system, driving a global conveyer belt of currents that carry oxygen, nutrients, carbon and heat. This constant churning supports all life on Earth and allows extraordinary diversity to thrive and flourish here. Where ocean currents bring nutrients to the surface, the startling blaze of phytoplankton that erupts can be seen from space. This is the base of the food chain, the source of half the oxygen we breathe, and as this organic frenzy dies off and sinks to the seabed it takes with it carbon that can be locked away in sediments. This natural process of ocean carbon removal – both biological and physical – keeps our world in balance, and has also allowed the sea to absorb more than a third of humanity’s carbon dioxide emissions.

Just as the ocean locks away carbon, it also locks away heat; the ocean has absorbed a staggering 93% of all the excess heat that has been trapped by greenhouse gases emitted as a result of human activities (like burning fossil fuels and deforesting our land). The ocean is a vital ally in our fight against climate change – but this does not come without a price. Warmer water fuels rising sea levels, intensified storms and strengthened marine heatwaves, all with serious consequences for human safety. At the same time, last year’s astonishing documentary Ocean by Sir David Attenborough starkly demonstrated the extent of other human pressures at sea, with factory fishing vessels, bottom trawlers and dredgers desecrating the seabed with incredulous extent across the entire globe, including almost all the world’s marine protected areas.

Restoring our deep relationship

The ferocity of global outrage is tragically tempered by the fact that all this is happening beyond our view. If we could see this industrial-scale destruction, we would not tolerate it. Recognising this, one of the 10 challenges underway within the current United Nations Ocean Decade is to ‘restore humanity’s relationship with the ocean’. An immense international effort is underway to do exactly this, and in the five years since it began there have been some very welcome changes. One of these is the ratification of the High Seas Treaty in 2025, the first ever international, legally-binding treaty to protect marine biodiversity in areas beyond national jurisdiction. This is critical in the implementation of the Global Biodiversity Framework to protect 30% of the land and sea by 2030.

In Wales, we are excited by the launch of a major ocean literacy project, Y Môr a Ni (The Sea and Us), which is bringing communities, organisations and government partners together to nurture a deeper connection with our seas, to improve access to the coast and enhance public and political investment in a healthy marine environment. This is part of our teaching at CAT too. Our MSc in Sustainability and Behaviour Change empowers students with the skills to make tangible change in their lives beyond their studies – in their communities and workplaces – to inspire living as ecological citizens, respecting the natural world around us. Students develop expertise in strategic environmental communication, with the opportunity to pursue research into ocean literacy and engagement through their dissertation.

This is a call to us all to be proud “Ocean Citizens”, understanding our connection to the ocean and taking responsibility for healthy seas and coasts, both through our personal daily actions and through our participation in democratic society. We need to mobilise communities with knowledge and with a deep emotional connection to collectively ensure we are active witnesses to the environmental damage inflicted at sea, and to push for meaningful and urgent protection. We invite you to join this global community of passionate ocean advocates, offering wider reach and new powerful narratives to ensure a healthy future for our seas.

About the author

Cathy is a visiting lecturer at CAT’s Graduate School of the Environment, teaching ocean science, communication, and public and policy engagement across several modules. She has recently taken up a new role at Natural Resources Wales as a Specialist Advisor on Marine Water Quality and will be giving a public lecture at CAT on 9 March as part of the Ecosystems and Ecosystem Services module. You can sign up to attend at cat.org.uk/event/public-lecture/