Fish Watching, Down Under: Part 1

In Two Wrecks, parts 1 and 2, I wrote about two spectacular and fish-filled shipwrecks in Australia: the Nord and the Yongala. Both of these wrecks are regularly visited by commercial dive operations, and so all advanced divers could, if they so wished, visit them on a trip to Australia. But now I would like to tell the story of the Lake Illawara, a recent wreck in Tasmania. But alas, the Lake Illawara is neither fish-filled nor spectacular. And in addition, I am almost certain that no one who reads this article will ever have the opportunity visit her; as it was only through the most unusual set of circumstances that I did, and thus became one of only a handful of people who ever has. This article is therefore of no use to the prospective underwater tourist selecting potential vacation spots.

All this explains why I didn’t include it in the original series of articles. So why write about it now? Well, you’ll still want to know about it if you ever visit Tasmania since it’s an important part of their recent history, and her sinking still affects the lives of all the people living in Hobart. It is also a very interesting story.

The story begins with the opening of the beautiful Tasman Bridge in 1964. The Tasman Bridge is a graceful 1.5km long, five lane, concrete-arch span that crosses the estuary of the Derwent River, thus connecting the city of Hobart (the capital city of Tasmania) with the townships on the eastern shore. Before that time one either crossed the estuary with a ferry or drove some 35km to the north to cross the river before it widens out.

Fast-forward eleven years to a foggy night, 5 January 1975. A bulk ore carrier, the Lake Illawarra, was on her way upstream to the zinc refinery about 5 km up the estuary. But she rammed one of the bridge’s 25m high concrete pylons, bringing down a section of the bridge onto the boat’s deck. The boat, already laded with ore and low in the water, sank immediately upon impact of the 700 tonnes of concrete from the bridge span. But most of the crew, including the captain, were either rescued later or swam to shore on their own. However, several cars travelling on the bridge fell into the gap in the bridge surface. They would either splash into the water 25m below, or else crash onto the boat deck. Several other people managed to narrowly escape this fate, as two more cars barely stopped in time and were left hanging with their front wheels dangling in the air. One of these cars, still belonging to its original owner, was to be featured in a TV news story in 1997 that celebrated the 20th anniversary of the bridge reopening.

Twelve people, including seven ship’s crewmen and five people in cars, were killed.

The Lake Illawara was deemed unsalvageable because of the close proximity of the hull to the remaining bridge. She was left where she lay.

The bridge remained closed for over two years, finally reopening in October 1977. In the meantime, the long-disused ferries were pressed back into temporary service. A temporary floating bridge was also built about 10 km to the north, and it was (some years later) replaced by a second permanent bridge across the Derwent. Several new ferries also had to be built for temporary service. The shipwright who built most of them used the revenue to build up his business into one of Tasmania’s largest locally owned corporations: a high-speed ferry builder with world-wide sales and a reputation for cutting edge design and performance. One of their ferries holds the Trans-Atlantic speed record for a passenger vessel. However the boom for the local ferry industry turned out to be a bust for east-shore residents, as they were faced with either long drives or ferry waits, and their property values crumbled. They have never fully recovered.

The location of the wreck is easily seen on the photograph of the Tasman Bridge. The picture was taken on the eastern shore, just north of the bridge. If you follow along the row of pylons supporting the bridge you will see two “double wide” pylon spacings; one directly under the highest point of the bridge and the second about half way between the highest point of the bridge and the near shore. These two gaps are the shipping lanes for freighter traffic moving up and down the estuary. The Lake Illawarra is under the gap closer to shore, although you naturally can’t see it since its resting on the bottom in 35m of water.

Ships moving up estuary still pass over the wreck, so no unregulated boat traffic is allowed over her. And parking a dive boat in the middle of the shipping lane is of course right out, so that is why you are unlikely to ever be able to dive there.

However, while living in Hobart I was a member of the University of Tasmania Underwater Club; an organization of hard-drinking and slightly off-kilter scuba divers and snorkelers. John, my dive buddy in the club, had always wanted to dive the wreck and thought he could get permission to visit it for the club. As an official organization, at least as far as the Hobart Ports Corporation was concerned, John’s request was considered and we were finally granted permission after he got the five necessary signatures, including one from the highway department (?).

We were given our choice of two-hour windows when we could park above the wreck without getting run over by any passing freighters. But we needed a window when the tide was slack and we were all off school, so we had to wait almost three months before a Saturday afternoon break in freighter traffic would coincide with a low current.

When the day finally arrived it dawned bright and clear. It was May, late autumn, but the weather was certainly warm enough at about 15C. We gathered at the university to collect the club’s 5m power boat and trailer, then headed to the boat ramp at the commercial dock. We were going to dive in three groups of four, and I was in the second group. While waiting on shore for the first group to return we amused ourselves by jumping off a 10m high scaffold into the water.

After 45 minutes the first group returned and we finally headed out to the wreck site, about 2km away. There wasn’t much wind, but the waves were still big enough to bounce the small boat around. When we reached the bridge that towered over us, the boat seemed even smaller.

The wreck showed up immediately on our depth finder, with the top of her bridge 15m below the surface and her deck 5m below that. We dropped an anchor onto the deck and when it snagged on something (a railing as it turned out) we were ready to dive. But the surface current was very strong, making me think we had miscalculated the current tables. The dive boat was taught to an anchor line that led down at a 45° angle: not very promising. However, the current was confined to the surface, and the water below a depth of 10m was very still.

Unfortunately the water clarity in the Derwent estuary is nothing short of atrocious.

The Derwent River is a “black water” stream: with soft (almost zero-hardness) water stained dark with tree tannins and peat. However, she’s polluted by a pulp and paper mill, the zinc refinery, and the untreated sewage that still pours into her. Her nutrient-laden water creates a bloom of algae when it mixes with the salt water of the estuary.

The environmental degradation of the estuary is quite saddening, as the estuaries of other black water rivers in Tasmania are the sites of fabulous and rare ecosystems. The layer of dark freshwater that overlies the dense, cold seawater of the Southern Ocean creates a uniquely dark but well-oxygenated environment close to the surface. Deep-water invertebrate species and calcareous algae are therefore found much closer to the surface than in other areas. Undisturbed examples of this type of environment, such as Port Davy in the remote south-west corner of the island, attract scientists, photographers, and divers from all over the world. But as the largest such estuary, the Derwent was undoubtedly the finest example of this special environment before it was lost under the weight of tons of accumulated pulp fiber and raw sewage.

Because of the anticipated poor conditions, everyone who had signed up to dive the Lake Illawarra had to do a preliminary “Braille dive” a couple of weeks earlier. This dive was done under supervision in shallow water (but poor visibility) at a site down stream of the bridge. This was to make sure no prospective adventurers would panic in the low visibility conditions of the wreck, since panicking at that depth is potentially very dangerous. So I had some idea what to expect, but despite the preliminary training dive – not to mention a lot of experience diving in British Columbian soup – I was quite surprised about how bad the visibility actually was at depth.

The fibers from the pulp mill have (over the years) filled the deepest channel of the estuary, and so the ship now sits in 10m of semi-suspended black organic goo; enough to cover the hull up to about half way up its side. You can stick you arm into this goo without feeling any resistance whatsoever, but when you draw it away, your arm comes back covered in black. The goo is of course completely opaque. I have been told you can swim right through this stuff and go right under the hull, but that would border on insane, not to mention pointless as you wouldn’t be able see anything anyway.

Above the goo layer the visibility is not exactly zero, but it is abysmal. But if you looked really hard and the light was just right, you could see your feet. Clumps of living and non-living organic material (mostly unidentifiable) floated in the water. And it was dark. Because of the time of year, the sun angle was quite low, and so the light penetration, even if the water had been clear, would have been poor. But with the naturally dark-stained water made even darker by the muck, diving lights were mandatory despite the brilliant sunshine topside. And because of the lack of water clarity our dive lights simply illuminated the goop in the water rather than the ship: it was like trying to drive through a snowstorm with your high beams on.

I was surprised to find no evidence of damage to the hull, or any sign of the concrete block that landed on top of the ship. Presumably the block landed off center, and then slid off the deck into the goo layer after it pushed the ship under the water. There was no sign of any of the cars either.

The wreck, only 21 years old at the time, was also in reasonably unaltered (meaning boring) condition. The ship’s paint was still clearly visible under a surface layer of gunk, and besides a coating of dirty rust-colored algae, not much life had taken over the surface.

But the wreck, perhaps surprisingly, was not completely devoid of life. The water below the first five meters is almost 100% seawater, with practically no mixing with the freshwater layer flowing above. So sea creatures are found on the wreck. Most surprising is that we saw some crayfish (Jasus novaehollandiae). Crayfish (or more properly, rock lobsters) are quite delicious and are a valuable commercial catch in southern Australian waters, but one would not be wise to eat those particular examples; maybe after the zinc refinery shuts down for a few centuries. There was also some schools of small fish swimming around as well, but the only ones I could identify were the blotch-tailed trachinops (Trachinops caudimaculatus), which are a very common goby-like fish on southern Tasmanian reefs. And there was even some benthic invertebrate life in the form of yellow colonial anemones starting to appear in some patches. These animals can create spectacular yellow “shag” carpets over the rocks in more pristine environments, but the small colonies that had taken hold on the Lake Illawarra were as dingy and dirty as the rest of the wreck. It was nice to see them though.

Now don’t get me wrong: by all reasonable criteria, the Lake Illawarra is a terrible dive. All the muck down there and the relative sterility of wreck itself means that this is hardly an underwater showpiece. But I really had a great time that day: some of the most fun I have ever had on the water. The day was fun for the adventure: diving in difficult conditions to see an important part of the local history; one that few Tasmanians ever have the chance to see. It was not an opportunity to be missed. ?