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The Amoco Cádiz
The Amoco Cádiz, an American oil tanker registered under the Liberian flag, can claim to be the world's largest accessible sunken wreck, lying at a depth of just 35 metres. Measuring 334 metres in length with a displacement exceeding 250,000 tonnes, this colossal wreck rests about three miles off Portsall harbour in French Brittany, among reefs known as the Rochers de Portsall.
Sunk in 1978, its wreckage constituted one of the worst ecological catastrophes in maritime history. Approximately 223,000 tonnes of crude oil were dispersed by tides and currents along 400 kilometres of Atlantic coastline bordering the English Channel. Due to rough seas, pumping oil from the tanks proved impossible.
The spill devastated the marine ecosystem, contaminating the area for over five years and killing thousands of seabirds and marine species. Cleanup operations continued throughout this period, gradually fading the disaster from memory. The area has nearly fully recovered, with marine life once again colonising the seabed, slowly consuming this strange metallic giant.
The Disaster
After crossing the Atlantic and entering the English Channel, the vessel encountered a violent storm with southwesterly winds exceeding 100 kilometres per hour.
In this part of the North Atlantic, currents surpassing 10 knots (18 km/h) and hurricane-force winds creating waves over five metres high have claimed thousands of vessels throughout history.
On the morning of 16 March 1978, while navigating off the coast of Brittany's Ouessant Island, the ship's hydraulic steering system failed. Drifting helplessly in the storm, it issued a radio distress call.
The German tugboat Pacific, commanded by Captain Hartmut Weinert, responded. After tense negotiations about salvage terms between Weinert and the Amoco Cádiz's Italian captain, Pasquale Berdari, attempts were made to tow the tanker away from shore. However, the tow lines snapped, hastening the inevitable disaster. After grounding on the Rochers de Portsall reefs, the ship broke in two, spilling its deadly cargo into the rich Atlantic waters.
For over a year, the Amoco Cádiz's bow remained visible above water, pointing skyward as if resisting complete submersion. It eventually sank, and today its remains lie at 35 metres depth.
Diving the Colossus
Before considering a dive, it's crucial to know that diving is prohibited throughout the area without special permission from French authorities - permits not granted to recreational divers. Many unexploded charges remain from 1978 when the French Navy dropped explosives from helicopters to breach the hull and accelerate oil drainage. Additionally, the depth and strong currents complicate diving and decompression stops, making this strictly for highly experienced divers.
The optimal diving window occurs during the tidal change, as high tide transitions to low tide.
This approximately one-hour period brings slightly calmer currents, allowing partial wreck exploration - seeing the entire wreck is virtually impossible due to its size; multiple dives would be required.
Descending, divers first encounter the stern mirror just 5 metres below the surface. Sheltering from currents along the port side, one can explore decks carpeted with kelp weaving through oil pipelines - kilometres of tubing that once transported black gold between the Amoco Cádiz's tanks.
The port side rests on Atlantic sands that gradually consume the hull's remains. Powerful waves shift sand and seaweed unpredictably. Maintaining position proves difficult due to water pressure against the hull. Another hazard is the siphon effect, which can suck divers through hatches or holes when waves create pressure differentials.
Countless small fish shelter among the seaweed-covered steel plates, while schools of anchovies and sardines form shimmering clouds in the blue.
Exit requires returning sternward, where decompression stops can be made while holding the wreck's structure.
Meticulous dive planning is essential as exploring the entire wreck is impossible. Multiple dives would be needed to appreciate this immense wreck fully.
Three Decades Later
After thirty years, the area's flora and fauna have only partially recovered. Disasters like the Amoco Cádiz continue haunting French coasts - in 1999, the Erika spilled 8,000 tonnes of crude, bringing renewed devastation to Atlantic waters.
Despite modifying traffic separation systems and improving coastguard coordination, French authorities struggle to address this ongoing threat to marine life.
