Watch the report by ITV's West Wales reporter Jess Main
Just after 8pm on 15 February 1996, an oil tanker called Sea Empress ran aground off the coast of Pembrokeshire. It was the beginning of what was to become one of Britain's worst environmental disasters.
The supertanker, loaded with more than 130,000 tonnes of crude oil, was near Milford Haven, en route to the Texaco oil refinery when it hit rocks near St.Ann's Head.
Thousands of tonnes of crude oil started to spill into the sea.
Over the course of the next week, 72,000 tonnes of it made its way around the Pembrokeshire coastline, killing thousands of sea birds and contaminating beaches.Maria Evans from Amroth remembers it well.
She runs Tinker's Hill Bird Rescue Centre, and was part of the clean-up at the time.
She said the birds were "like a blob of black oil.""You might have seen the beak or the eyes but it was just a blob of black oil. I still can't believe the numbers of birds that we had like that, it was appalling," she said.
Over the coming days rescue teams battled the winter weather and coastal elements, as they tried to bring the Sea Empress under control.
It took another seven days before they managed it. By which time, almost 72,000 tonnes of oil had escaped.Thousands of sea birds were found dead on the shores or covered in oil, despite volunteers' attempts to save as many as possible.
Common Scoter ducks were the main victims, though their population has since made a significant recovery.
Cliff Benson now runs The Sea Trust, but he remembers vividly the sight of the ducks on the beach at Pendine.
"The smell of the oil was just unbelievable, and there was all this thick black sludge coming up the beach with hundreds maybe thousands of Scoter ducks," he said.
"It was kind of apocalyptic really, it was horrible."
Cliff recalls how he, along with others, did everything they could to help the clean-up effort, but said it was an emotional time.
The oil also had a devastating impact on local industries such as shellfish and lobster fishing, which was banned for months after the disaster.Hundreds of people including, including volunteers, worked to clean up the 120 miles of contaminated coastline, at a cost of £60 million, which was being watched by the world's media.
An official report blamed pilot error for the tanker’s initial grounding, and said other factors such as bad weather, and a lack of understanding of the tidal currents were also at play.
Since then, multiple safeguards have been put in place at the port to prevent a repeat event.
Today to look at Pembrokeshire's beaches, it's almost as if it never happened, and environmental experts say the area has made a full recovery.
Jon Moore is an Environmental Consultant, working on oil spills around the world.
"I don't know where it ranks in size in terms of spills that have been around the world, but it's probably in the top 20," he said.
Jon says in some ways the disaster could have been much worse.
"It was lucky that the majority of it went outside of the Haven, where there's lots more wave action and water movement to break it up."
Twenty five years on and the effects of the spill, he says, would be hard to find."We really didn't find effects much beyond six or seven years after the spill, you'd struggle to find any effects now but bird population is possibly the exception."
Harbourmaster at the Port of Milford Haven Mike Ryan said the Sea Empress incident was "hugely significant" for the area, UK shipping ports and the entire shipping industry.He said since the incident, multiple safeguards had been put in place, including the introduction of a national Port Marine Safety Code, to prevent anything similar from happening again.
It was a day, and a sight many will remember for years to come, threatening to damage Wales for generations.
While many would agree it could have been a lot worse, those who remember it say it is important it is never forgotten.