Ski Run takes its name from its layout: from the reef edge at around 15 m a pale sand chute runs down the slope like a ski run, and Diveplanit's Cocos page describes a 'sandshute to drop-off' dive that matches it. The official tourism listing calls it a spectacular site and gives a range of 15–40 m. The dive starts at the edge of the reef, where hard and soft coral give way to sand, and descends to a bommie covered with glassfish – dense, shimmering curtains of small silver fish that part and re-form as divers move through them, and which in turn draw in predators.

Trevally hunt the glassfish schools, cutting through them in bursts, and the interplay between predator and prey is the character of the site. On the sand slope itself, whitetip reef sharks rest on the bottom, often in small groups, and the colony of garden eels here includes what the official listing calls 'extra-long' eels, standing tall out of the sand in the current. Because much of the interest is on sand and around a single structure rather than along a coral wall, Ski Run makes a good contrast to its neighbours Cabbage Patch and Rose Wall.

Depth is the defining feature: the bommie sits at the kind of depth where no-decompression time shortens quickly, and the slope continues to 40 m and beyond, so this is better suited to divers with Advanced certification or comparable experience. Visibility on the north-western side is usually 20–30 m or better, and on the incoming tide the water can be exceptionally clear, making the descent down the sand chute one of the more atmospheric entries on Cocos. Current varies with the tide through the nearby Western Boat Passage.

The dive rewards patience – settling at the bommie and letting the glassfish and trevally show unfolds better than covering ground. For photographers, the glassfish bommie with sunlight from above is the shot, and wide-angle is the lens to bring.

Fly to West Island on the twice-weekly Virgin Australia service from Perth (usually routed via Christmas Island; allow 7–10 days on the islands to absorb weather and flight delays). Cocos Dive collects divers from West Island accommodation in the morning (pickup around 8 am, departure about 9 am) and runs its boats from West Island into the lagoon. The north-western sites around Horsburgh Island are among the closest to West Island: the boat runs north up the inside of the lagoon past the northern tip of West Island towards Horsburgh, a short, usually sheltered ride.

Moorings or live-boat drops are used; there is no shore access. The lunchtime surface interval is normally taken on the beach at Direction Island before the second dive.

Cocos has two seasons. The south-east trades blow steadily from roughly April/May to October, often 15–25 knots, which chops up the lagoon and pushes swell onto the eastern and southern outer reefs; divers are then kept to sheltered sites. The doldrum season (November to March/April) brings lighter, variable winds, flatter seas and the widest choice of outer-reef sites, and is the best time to dive, though it is also the tropical cyclone season and squalls pass through.

The north-western rim sits in the lee of the atoll during south-east trade winds, so these sites are often the ones that stay diveable when the trades blow; a strong westerly or north-westerly swell (uncommon, mostly in the doldrum season or with passing cyclones) closes them. Tidal flow through the Western Boat Passage near Horsburgh sets up currents along the reef edge, so dives are timed with the tide; visibility is best on the incoming tide when clear oceanic water pushes in.

Descend at the reef edge around 15 m, then follow the sand slope down to the glassfish-covered bommie. Circle the bommie between 20 and 30 m, check the sand around it for garden eels and resting whitetips, and set a firm maximum depth before starting – the slope keeps going past 40 m. Return up the slope to the reef edge and finish with a long safety stop in the shallows.

Nitrox, if available, would extend bottom time at 20–30 m; confirm with Cocos Dive before travel.

Cocos Dive (Dieter Gerhard, West Island, operating since 1990) is the only scuba operator on the islands and the only way to dive this site. It runs seasonal two-dive day trips with lunch and a surface interval on Direction Island, maximum 10 divers per trip; sites are chosen on the day according to wind, tide and diver experience. Trips book out well ahead and courses are currently suspended, so arrive certified.