Ocean liners have long stood as pinnacles of maritime design—grand in scale, rich in detail, and powerful symbols of national prestige. Ships like Britannic, Andrea Doria, Lusitania, and Wilhelm Gustloff are now iconic wrecks—coveted destinations for technical divers seeking history beneath the waves. Few places rival the British Isles for wreck diving, where a turbulent maritime past, two World Wars, and hazardous shipping routes have left the seafloor scattered with dozens of diveable liners.

While most of these wrecks have been found and explored, a handful remain elusive. In late 2024, UK-based dive team Darkstar pushed that list closer to completion when they discovered the long-lost HMS Marmora, resting in 120 meters (394 ft) of water, 70 nautical miles off the Irish coast.

Built by Harland & Wolff in Belfast and launched in 1903, Marmora was a 168-meter (550 ft), 10,500 GRT passenger liner operated by the Peninsular and Oriental Steam Navigation Company (P&O). She sailed routes to Australia and India until 1914, when the Admiralty requisitioned her as an armed merchant cruiser. Outfitted with eight 4.7” guns and depth charge launchers, she joined convoy escort duties during World War I.

On July 23, 1918, German submarine UB-64 fired two torpedoes into Marmora while she was escorting a convoy. She sank within 30 minutes. Ten men died—most likely killed by the initial explosion.

Founded and led by Mark Dixon, Darkstar is the UK’s premier deep diving team, recently marking their 25th anniversary. Their track record includes pioneering dives on some of the most technically demanding wrecks in British waters: Empress of Britain (165 m), HMS Transylvania (130 m), SS Arabic (115 m), and USS Jacob Jones (115 m).

The team closely monitors seabed survey data released by UK and Irish authorities, using it to identify targets by shape, size, and coordinates. This strategy paid off in 2022 when they became the first to dive the SS Missanabie (100 m), another 10,000 GRT liner sunk in 1918.

When Darkstar identified another large, promising sonar return further west, they knew a launch from Ireland was the only viable option. In September 2024, they assembled near Cork, Ireland. During the nine-day expedition, three divers made the journey from Plymouth aboard their dive vessel Darkstar, stopping midway to dive an unidentified wreck at 102 m—possibly The Greek, based on Anglo-Greek crockery found on site.

But the road to Marmora proved difficult.

Weather is always a wildcard in Atlantic diving. Though conditions weren’t severe enough to cancel operations entirely, rough seas made long offshore runs risky. The team instead explored several nearby wrecks in the 70–90 m range, though poor visibility made identification difficult—albeit revealing clues in the form of shipping-line crockery.

Then came mechanical issues. The boat needed new batteries, wiring loom repairs, and even a replacement starter motor—which failed on the final planned dive day. Determined not to be beaten, the crew scrambled to source and install a new motor from a local garage.

With only the late slack tide remaining, the crew prepared for a long and uncertain day. The 70-nm transit took four hours, but once on site, the excitement was palpable. The massive outline of Marmora appeared clearly on sonar. Calm surface conditions and clear prep made for a smooth drop.

I was fortunate to be among the first pair to descend, tasked with securing the lazy shot to a prusik loop at 45 m. Though light faded rapidly past 100 m, visibility remained excellent. Unfortunately, both my video and primary lights failed in sequence. Relying on a backup torch stored in my drysuit pocket, I pushed forward using a single functioning video light.

We knew from sonar that the wreck was lying on her side, but not which one. After deploying strobes, I chose to head starboard. The wreck was heavily broken—likely depth-charged during WWII—and orientation proved difficult. My scooter then ingested some netting and stopped abruptly, though I managed to clear it quickly.

Then, a breakthrough—a massive bronze propeller loomed out of the darkness. Realizing I’d reached the stern rather than the bow, I reversed course. Along the way I encountered another diver—also heading the wrong way. As we pressed forward, the wreckage revealed itself. I found the bridge, intact, with a bridge telegraph still in place, surrounded by non-ferrous artifacts.

In British waters, discoveries like this are rare. To be the first person to lay eyes on these items since 1918 was a humbling, extraordinary experience.

Time, however, was short. My four-hour runtime limit was nearing. As I turned to ascend, my last video light failed, leaving me in total darkness. Thankfully, my strobes—though sunken lower than expected due to slackening tide—guided me back. I descended briefly to retrieve them, which cost me an additional 15 minutes of decompression.

At last, I reached my first deco stop at 66 m. Four hours after descent, I surfaced to calm seas and quiet celebration aboard Darkstar. The rest of the team followed soon after, just as the light faded.

Was it really Marmora? The wreck was clearly an ocean liner, but there were other contenders—such as RMS Hesperian and SS Arabic, both sunk nearby. The key identifiers, though, were unmistakable: armaments (neither Hesperian nor Arabic were armed) and P&O-marked artifacts on the seabed.

We had found her.

As night fell and celebration began—with whiskey and high spirits—our luck turned. One of Darkstar’s engines began to fail. Oil pressure dropped. On inspection, we found the engine compartment coated in oil and echoing with ominous clanks. Thankfully, the second engine remained functional, but our speed was halved. ETA: 0200.

Logistics soon unraveled. Our Airbnb check-out was imminent, some team members had booked ferries, and we faced the reality that Darkstar wouldn’t be sailing home anytime soon.

Teamwork carried the day. Upon arrival, everyone jumped into action—relocating gear, managing transport, and coordinating van pickups. Two of us drove to Bristol and returned to Ireland for the kit. Three ferries and hundreds of miles later, we were home.

The boat was less lucky. Weeks later, it crossed the Irish Sea to Milford Haven on one engine.

That day was a microcosm of wreck diving: exhilarating highs and frustrating lows. From the thrill of discovering an untouched wartime liner to the chaos of mechanical failure, it was unforgettable.

If there’s one lesson to take from it all, it’s this: diving gives with one hand and takes with the other.