12/10/2025
🌊 Our Warming Sea - From Octopus to Orca’s - What is marine diversity showing us?
The seas around the UK are changing and this summer, the sea has been…well, warmer.
I’ve been diving the south coast for many years, and this year has felt different. In the news, some new species have appeared in UK waters, alongside some unexpected encounters: fin and pilot whales, leatherback turtles, jellyfish blooms, blue-fin tuna flashing past and even orcas were spotted off the coast of Cornwall.
For photographers and ocean lovers, these changes are thrilling and thought-provoking but what we’re seeing through our lenses isn’t just chance - it’s a glimpse into a shifting marine world.
So, whilst it’s been a year of remarkable marine visitors, both exciting and beautiful – just beneath the surface - a little unsettling too.
Each encounter tells a bigger story about our changing seas, warming waters, and the way marine life is adapting right before our eyes.
Through photography, we’re not only witnessing these changes, but also documenting it at a crucial moment in time.
🌡 The Warming Sea
According to the BBC sea temperatures reached up to 4°C above normal, with the average surface sea temperature of UK waters - in the seven months to the end of July 0.2°C higher than any year since 1980.¹
This kind of spike is being described by scientists as part of a marine heatwave - a sign of a rapidly changing climate.
Warmer waters are reshaping the ecological map of our coastline. As sea temperatures rise and currents shift, marine species are moving. Creatures more often associated with temperate or distant seas are appearing in UK waters in growing numbers, sometimes in places they’ve rarely been seen before.
🫧 A Year of Remarkable Sightings
Some of these stories have made national headlines; others come from swimmers, divers and coastal communities simply paying attention:
• Octopus have been seen in unusually high numbers this year, with their eggs surviving the cold winter waters in higher numbers.
• Blue and basking sharks have been appearing closer to shore, with increased sightings reported through the summer.
• A pair of Orcas off Cornwall gave onlookers a rare and magical moment.
• A rare Fin Whale was seen off Falmouth in September.
• Pilot Whales were seen off Plymouth.
• A Leatherback turtle was spotted off the Devon.
• Atlantic bluefin tuna have been seen more often along the south coast.
• Mauve jellyfish have all been reported in UK waters in higher numbers (swarms) than usual this season.
Individually, these sightings are thrilling. Collectively, they tell us something important: the sea is not static. It is dynamic, alive, and is responding to change - both natural and human-driven.
And for those of us who spend time in the water, the shift is tangible. The sea has quite literally felt warmer, noticeably to me at times this summer during swims and dives.
🌊 The Double-Edged Sword
There’s huge joy in witnessing this marine diversity and the marine life visiting our shores or making a home. It reminds us how vibrant and resilient the ocean can be. But it’s also comes with a warning.
Warming seas, altered habitats, and shifting species distributions are signs of a changing climate playing out in real time. Some species may thrive in these new conditions; others may struggle.
Ecosystems could become unstable, food chains disrupted, balances altered.
Celebration and concern, side by side.
The arrival of these incredible species is thrilling, but it’s also a quiet alarm bell. Warmer seas are reshaping ecosystems in real time — and while we celebrate these sightings, we can’t ignore the forces driving them.
🌿 Resilience and Adaptation
The movement of marine species around our coastline is, at its heart, a story of adaption and resilience. Faced with changing conditions, ocean life adjusts, travels, finds new ways to survive.
Species like the octopus, jellyfish and blue fin tuna aren’t just passing visitors — they’re proof of how life responds to change.
They’ve followed or adapted to warmer seas, travelled vast distances, and adapted to new conditions to survive.
Their journeys are reminders that resilience isn’t about resisting change; it’s about moving with it, finding new pathways, and living and thriving, even with uncertainty.
There’s something in that for us too. As humans, we’re being called to adapt — to listen more closely to our environments, to notice what’s shifting, and to find our own adaption and resilience in responses to change.
For me, as a marine life photographer noticing these changes has deepened my sense of connection with the water. Each encounter feels like both a gift and a warning: the sea is alive, it’s changing, and it’s inviting us to pay attention.
🫧 A Ripple of Awareness
Noticing might seem like a small thing, but it’s where change begins. When we observe, we see, when we see we care, and when we care, we act.
The sea is sending us signals — in pilot whales, leatherbacks, sharks, octopuses and orcas. And it’s up to us to listen.
Sources
¹ BBC News & Euronews, “UK seas are up to 4 °C above average this summer,” May 2025.
https://www.bbc.co.uk/news/articles/cglz8w0ypkyo
https://www.bbc.co.uk/news/articles/c05enyryqvmo
https://www.euronews.com/green/2025/05/22/uk-seas-are-unusually-hot-and-scientists-say-the-heatwave-could-just-be-getting-started
² The Guardian, “Marine hot spot could change makeup of British fish species,” Feb 2025.
https://www.theguardian.com/news/2025/feb/28/weatherwatch-marine-hot-spot-could-change-makeup-of-british-fish-species
Pilot Whale footage from my personal archive.
Copyright Stephanie Pettitt 2025
