The Catalina JX435 site is the wreck of a Royal Air Force flying boat that crashed in the Cocos lagoon at the end of the Second World War, and it is both a dive site and a war grave. According to the WA Museum's nomination of the site to the Commonwealth Heritage List, Catalina JX435 of 240 Squadron, based at Madras, was carrying materiel and fourteen people when it crashed on 27 June 1945 while landing at Cocos. The pilot attempted a downwind landing in rough seas; the aircraft overturned, broke apart and caught fire, and seven of those on board died.

Their bodies were never recovered. Cocos was a strategic mid-ocean base in 1944–45, with an airstrip on West Island and flying boats operating in the lagoon, and the Catalina is a tangible reminder of that period. The wreckage lies in 4–6 m between Direction and Horsburgh Islands.

The aircraft inverted and broke up on impact, so there is no intact airframe; instead the two Pratt & Whitney engines and propellers mark the impact point, and fuselage, wing and tail components are spread in a classic wreckage plume extending about 600 m south-west, most of the fuselage now missing. Cyclones have added to the break-up over the decades. Dive Pacific's Cocos feature notes the site can be explored in two dives and that the debris descends from a few metres onto seagrass beds.

The shallow depth gives long dives, and the scattered aluminium parts, gradually being colonised, host reef fish, while the surrounding seagrass is feeding ground for turtles. For divers with an interest in aviation or military history it is one of the most poignant sites in the Indian Ocean territories. Visitors should treat it as a memorial: nothing may be touched or removed.

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 Catalina lies in the shallow northern lagoon (Port Refuge) between Direction and Horsburgh Islands, on seagrass and sand.

It is reached only by boat with Cocos Dive, which can cover the debris field in about two dives. No shore access; the nearest landing is Direction Island.

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.

Port Refuge, the north-western corner of the lagoon between Horsburgh and Direction Islands, is shallow and protected from ocean swell by the reef, but in strong trades it becomes choppy and the fine sand stirs up, lowering visibility. Dive or snorkel on calm days and around high tide on the incoming flow for the clearest water; tidal streams through the northern passages can be noticeable at mid-tide.

Start at the impact point, where the two Pratt & Whitney engines and propellers lie, then follow the debris plume south-west across sand and seagrass. The field is about 600 m long, so plan two dives or a slow drift with a boat following. Treat the site as a war grave.

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.