A vibrant world of life under Swanage Pier is becoming more intense as sea temperatures warm up – but for those in the know, the idyllic location has always been one of the best dives in the world.
Members of the Isle of Purbeck Sub Aqua Club say that while local waters have always teemed with life, the species are slowly becoming more exotic – and the wealth of wildlife beneath the waves now makes Swanage Pier a bucket list dive site.
A common octopus has ironically become one of Dorset’s rarest residents
A curious cuttlefish has his photo taken beneath the piles of Swanage Pier
Previously almost unknown
One of its divers, award winning underwater photographer Paul Pettitt, has recently photographed an octopus off the Dorset coast – in a location he is determined to keep secret to protect the animal.
Although the species is called a common octopus, they are anything but common in the waters around Swanage – previously, Cornwall and Devon have been the northernmost limits of the creature, more often found off the coasts of France, Portugal and Spain.
The octopus now joins a growing list of sealife being spotted in Dorset which were previously almost unknown, like the anemone shrimp, the black faced blenny, John Dory and bluefin tuna.
And with other sightings offshore of barrel jellyfish, Risso’s dolphins, sunfish and porbeagle shark, the county is becoming talked about both nationally and internationally.
Swanage Pier is teeming with life as shoals of fish arrive with warmer seas
Some visitors to Swanage Bay look more suited to the ocean depths
“Definitely a bucket list dive”
Paul Pettitt said:
“Swanage is the home of British diving. The first dive school in the country opened here in 1958, when Bob and Dennis Wright opened Divers Down – there are so many people who did their first dive under the pier and today it’s a definitely a bucket list dive.
“British waters are very colourful, but people just don’t think that. For me, British diving is better than anywhere in the world. It is subjective, but I’ve had some of my best dives under Swanage Pier and my best dives in the world in this country.
“We do tend to keep the location of some things we see secret. If there is something interesting under the pier like lumpsuckers, we won’t mention it until a month after they’ve left because we don’t want people going under there in search of them.
“We are divers, the only thing we hunt with are cameras or our eyes. We are very careful about mentioning where we see animals because we do have a problem here with spear fishermen and we don’t mix. They want to kill it, we want to watch it.”
There’s a riot of colour to be seen beneath the pier
Jellyfish are becoming ever more common visitors to the pier
“An interesting phenomena”
Veteran member of the Isle of Purbeck Sub Aqua Club, Nick Reed, said:
“The octopus is an interesting phenomena – 30 years ago I hadn’t seen any at all, but people are starting to see them in Cornwall and Paul has now photographed one in the Dorset seas.
“Is that possibly due to climate change or something else like overfishing at sea, so they are starting to move closer to the shore to find food? I don’t know.
“That’s the trouble – people often say that an unusual species is being seen in Dorset, which we associate that with warm water, so therefore it’s climate change.
“One of the species that started coming under the pier about 15 years ago, the black faced blenny, is a southern species which is gradually working its way along the coast, and this year there are a lot more of them than there have been before.”
A sea gooseberry is pictured against bright colours on the pier’s beams
Just three metres beneath the waves, there’s a wealth of wildlife to be seen
“There’s always change going on”
Nick added:
“Then there’s the anemone shrimp which was first discovered on the mainland of the UK under Swanage Pier. Again, it’s more of a southern species which you would expect to find in the Channel Islands, but now they are established here, possibly an indication of climate change.
“But there are also cyclical, natural biological changes, subtle differences from year to year. When I first started diving 34 years ago, I was amazed at the number of spider crabs. They are still here, but you go through cycles – one year you’ll find the place crawling with spider crabs, the next year not so many.
“There is always change going on, that’s the important thing. It’s part of marine life. There’s a basic biological cycle going through the seasons and you will always get oddities coming in, but I think it’s probably fair to say that with the temperature warming up we are getting slightly different species at slightly different times of the year.”
Swanage has just experienced its annual May bloom, when currents bring up nutrients from the bottom of the sea as temperatures warm up, encouraging microscopic algae to multiply and turning the water bright green.
Now jellyfish, cuttlefish, pollock and bib are arriving in the area to feed, along with mackerel which will in turn attract dolphins, while shoals of sprat are set to arrive later in summer.
A John Dory on the seabed off Swanage, another fish better suited to warmer waters
A tompot blenny sitting in a pipe under Swanage Pier – the fish have become an attraction in their own right
“It’s a vibrant and wonderful world”
Alison Pettitt, an experienced diver and underwater photographer, said:
“It’s little wonder that Swanage attracts so many divers, it’s a vibrant and wonderful world, with so much marine life under Swanage Pier and all around the Dorset Coast.
“The pier is very accessible, you can park easily and get into the water easily, the marine life is concentrated under the pier so it is easy to find, and the structure of the pier gives a picture more context when you are photographing a marine animal.
“There’s a fish under the pier called a tompot blenny, it’s one of the things Swanage is famous for and which people will come here specifically to see – it has a funny looking face and is colourful and characterful.
“There are crabs, lobsters, sea slugs and cuttlefish, it can be teeming with life at this time of year, there are large shoals of fish in at the moment like sea smelt, and you can do this on your training dive, it’s really good for beginners.
“For more experienced divers, Swanage Pier gives access to hard boat diving to take divers out to the wrecks, or to do a drift dive of the bay, just 10 minutes out, where you might see dogfish, a variety of shark called tope, crabs, lobsters, undulate rays, and dead men’s fingers, which is a type of soft coral.”
Nick Reed (left) and Paul Pettitt (right) rate Swanage Pier as one of the best dives in the world
Fewer plants, more animals
Nick Reed added:
“Contrary to what you may believe, sea life thrives under the pier because of human interaction – the old pier, where hardly anyone ever goes, has very little life, it is all over here.
“It’s the effect of shading – on the old pier there’s hardly any shading, the water is three or four metres and there’s lots of weed growth.
“But because the main pier has lots of shading it cuts out the light and instead of getting lots of weed growing you get water conditions more akin to 10 metres deep with many more species – less plant growth, more animal growth.
“Even what you might think of as plant life on the legs are actually what we call animal turf, things like hydroids, bryozoans, all these tiny little creatures that live in colonies, and they are food for other animals and part of the wider food chain.”
Divers from the Isle of Purbeck Sub Aqua Club are carrying out a survey on the underwater structure of the pier
The clear waters around the pier make it a draw for all manner of water sports
Sustained climate change
Marine scientists at the Centre for Environment, Fisheries and Aquaculture Science have just revealed that in May 2025, unseasonably high temperatures warmed Dorset seas four degrees higher than usual.
They believe that sustained climate change could lead to gradual changes in sealife, with sharks, rays, jellyfish and octopuses becoming more common, while some native coral species could struggle to cope with changes.
Sarah Hodgson of the Wild Seas Centre in Kimmeridge said:
“Common octopus this year have had a bumper year with a number of sightings in Dorset, Devon and Cornwall. They generally tend to be less common in this country than other species of octopus and are more frequent in warmer climes.
“It could be an indication that our seas are warming and these species are able to survive and even thrive off the UK coast, so sightings are more abundant.”
The Wild Sea Centre at Kimmeridge and Dorset Wildlife Trust are always keen to hear about marine sightings
“Starting to see bluefin tuna”
Sarah Hodgson added:
“The anemone shrimp is quite a specialist species and Swanage Pier is one of the best places to go to see them, it is definitely a hotspot for this species which were first recorded in the UK in 2007.
“More recently we are starting to see bluefin tuna off the Dorset Coast once more, which is amazing – they are magnificent huge fish which had been virtually absent from our waters since the 1960s, partly due to pressures from overfishing and also likely the fluctuating sea temperatures which shifted their prey.
“Quite a few different species of whales and dolphins are recorded along the Dorset Coast, we have England’s only resident bottlenose dolphin population along the south coast, about 40 in total which split up into smaller foraging groups and head off in separate directions.
“They have been identified as a distinct resident group, although they do travel over quite a large range from Cornwall all the way along the coast to Sussex.”
Divers Down was the UK’s first diving school, as long ago as 1958
The sub aqua club lays wreaths annually at the site of sunken Valentine tanks in Swanage Bay where World War Two soldiers drowned
Further information
- Get involved with the Isle of Purbeck Sub Aqua Club on its website
- Join in family seashore adventures at the Kimmeridge Wild Seas Centre
