The Undola is one of the classic deep wrecks of southern Sydney: a small, complete collier sitting upright on the sand 2.5 km off Garie Beach with fish life that rivals any wreck on the coast. She was built by J. Fullerton and Co. of Paisley, Scotland, launched on 13 October 1909 for Coal Cliff Collieries and delivered to Sydney in January 1910 after a 74-day voyage.

At 41 m long and 8 m wide, with a 580 hp triple-expansion engine and two holds for about 420 tons of coal, she ran the South Coast coal trade from Coal Cliff, Bulli, Bellambi, Wollongong and Port Kembla into Sydney and was never a profitable ship. On 20 December 1918 she left Bellambi under Captain Arthur McDonald, fully loaded, just as a violent southerly buster swept up the coast with 44 mph winds and a temperature drop of more than 30°F in under two hours. She never reached the Heads.

Wreckage washed up at Cronulla and a lifebuoy confirmed the loss of all 11 crew; the likely cause is that she took water or her cargo shifted and she turned turtle, although wartime rumours of a German mine persisted. Today the Undola lies upright, bow to the north-east, in 43–45 m. She is lower and smaller than wrecks such as the Tuggerah or Kelloe, but largely intact and easy to understand.

The boiler stands up prominently amidships with the triple-expansion engine behind it; aft are the stern winch, the rudder post with its steering arm fallen to the sand, and the stern. Forward, hatches and hull sections lead to the bow winch. A famous porcelain toilet stamped 'Shanks & Co.

Ltd, Patentees, Victorian Pottery, Barrhead' is a favourite photo subject. The wreck is a fish magnet: clouds of bullseyes and nannygai inside the hull, yellowtail kingfish and seapike overhead, old man snapper, conger and moray eels in the plates, and occasional sunfish and seals. It is only for experienced deep divers comfortable at 45 m with good gas planning, ideally on nitrox-optimised or trimix deco gases, and suits those working through the southern Sydney deep-wreck circuit.

Boat only. Launch in Port Hacking (Gunnamatta Bay/Tonkin Park at Cronulla, Lilli Pilli or Grays Point ramps), run out past Jibbon Point and south along the Royal National Park cliffs to Garie Beach – about 12 km and 25–35 minutes in reasonable seas. Kurnell (Bonna Point) or the Botany Bay ramps are a longer alternative.

McFadyen's GPS mark is 34° 10.7418' S 151° 05.6332' E; the old transits line the mound at Cape Baily to the north with the pointy rock at the tip of Marley Point. Anchoring is awkward because of sand gaps between the boiler and bow – many crews drop a shot and hang a deco station. Charters are rare (Abyss's boat occasionally), so it is mostly a private-boat or club dive.

Fully exposed open-ocean site off the Royal National Park coast. Any significant southerly or easterly swell (over about 1.5–2 m) makes the run and the anchoring uncomfortable, and the wreck's own history is a reminder that southerly busters arrive fast in summer. North-east sea breezes build most afternoons from October to March, so go early.

The East Australian Current usually sets from the north here and can run at 1 knot or more at the surface while being slack on the bottom – use a shot line and a drifting deco station if it is running. Visibility is usually good (often 20 m+, 35 m recorded) but plankton blooms in spring can reduce it. Best days are winter westerlies with low swell.

Descend the shot to the boiler (the highest point), tie in, then swim forward past the forward hold and bow winch to the bow, return along the other side to the triple-expansion engine, stern winch, rudder post and fallen steering arm. The famous Shanks toilet is near the stern. With air, 12–15 minutes on the bottom is the practical limit before decompression becomes significant; ascend the shot and do staged stops on a hang line.

Deep air is possible but most teams now use trimix or EAN for deco. Plan 12–15 min bottom time on twin cylinders with a deco gas (EAN50) and a drifting or fixed hang line. Excellent rebreather dive.

Protected historic shipwreck.

Abyss Scuba Diving (Ramsgate) visits very rarely on its deep-wreck days; otherwise private boats and technical/wreck clubs (Sydney Wreck Divers, St George Scuba Club) from Port Hacking.