Olympia Maru

The main deck comes up at eighteen metres and stays there, which is what makes this wreck different from the rest of the fleet. She sits upright and level, her cargo bays open to the light, and a diver can hang over an open hold and see the bottom of it. The sand is at thirty, thirty-two in places, but you do not have to go down there and most dives do not.

The port flank is where the survey work slows down and so does the dive. Black coral, lettuce corals, white sponges, brown finger sponges with sea cucumbers wrapped around them, anemones with clownfish in them1. Big batfish work the bow, the stern and the mast. Scorpionfish sit everywhere on the wreck, and lionfish gather on the main deck in numbers that surprise people who came for the ship.

Inside, the favourite is the bow locker room, where the coiled cable that hauled the anchor is still on its drum. The holds are the other way in, big enough to swim through with the entrance behind you and daylight ahead. Navigation along the main deck is straightforward.

The ship is not tidy, though, and it is worth knowing why before you look at it. The upper deck is buckled and the masts lean out of true, because she burned for hours before she went down1. On the way back up you are swimming over deformed plating, not a clean deckline.

Every operator in Coron calls her a freighter. Her own service record says she was converted in 1941 into an Army auxiliary aeronautical repair ship, and that when the conversion finished the Army's 18th Shipping Air Depot was organised and carried aboard her2. She was a floating aircraft workshop with the unit to run it, which is a more interesting ship than a cargo hull and fits what this whole fleet was doing at Coron.

She is also the wreck Coron uses to make wreck divers, and the reasons are structural and not promotional. Upright hull, so nothing is rotated. Holds open to daylight, so the exit stays in sight. Calm water, unlike the shallow tanker on the other side of Busuanga, where a similar depth comes with a current that decides the dive for you.

And she is the one the bay dives after dark. Sleeping fish and turtles bedded into the structure, on a wreck whose layout is simple enough that darkness does not turn it into a maze3.

She was built at Nagasaki as a 5,612-ton cargo ship for a Tokyo owner and re-engined from steam to diesel in 1930. Two records-based accounts of her building disagree by seven years, so this page gives no build year. About 128 metres long, by the figure two independent sources converge on.

The Army requisitioned her in July 1941 and gave her a number. That September she went into the yard at Shimonoseki for conversion to an Army auxiliary aeronautical repair ship, finishing in October, and the Army's 18th Shipping Air Depot was formed and embarked aboard her2. That is the ship that came to Coron: not a freighter carrying supplies, but a workshop for aircraft with its unit aboard, alongside cargo for the occupation forces.

In September 1944 she was at Manila. She left with the convoy on the 22nd, reached Coron Bay the next day and anchored just west of Tangat Island. Carrier aircraft attacked the anchorage on the morning of the 24th. Accounts of the attack describe her already under way and trying to evade, hit in the engine room, then in the galley and the holds. Fire spread and burned for more than four hours, bending the midship section, and she went down by the stern2. The deformation a surveyor photographed in 2025 is the same fire, eighty-one years on1.

Then she lost her name for half a century. Divers knew her only as the Tangat wreck, after the island she lies beside, and the identification was not settled until the late 1990s3. In February 2026 she was the first ship named in the National Museum of the Philippines' announcement of six Coron wrecks whose photogrammetric scale models it had received4.

Have the guide show you the way in before you say yes. The holds here really are the forgiving kind, big and lit with the way out behind you, and that is precisely why this is the wreck where divers get led inside without much conversation. Coron has a documented case of divers taken into wrecks without wreck training and without a briefing that matched the dive. The openings on this ship are a property of the ship. Whether you are trained for what is behind them is a separate question, and it is yours.

Keep off the structure. Scorpionfish are common across the whole wreck, lionfish gather on the main deck, and there are stinging hydroids in the growth along the flank. Hover instead of settling, keep hoses and gauges tucked in through the openings, and the wreck stops being a contact problem.

Decide your working depth before you descend. Eighteen to twenty-four metres is a long, easy dive on the main deck. The sand at thirty to thirty-two is a different one with a different clock, and the deck edge is the only thing between them.

Nothing comes off her. She is over fifty years old, which makes everything on and in her state-owned cultural property under Republic Act No. 10066, and disturbing the site takes written authority and museum supervision5. That includes the anchor cable in the bow locker that everybody photographs.

If you dive her at night, treat it as a new dive and not the same one darker. And settle the evacuation question before you book, because no working recompression chamber is confirmed anywhere in Coron. A wreck that welcomes inexperienced divers does not come with a shorter chain to a chamber.