

Crack a Jack earns its name from the dense schools of jacks that sweep through the water column here, often accompanied by fusiliers and clouds of glass fish that part around you as you descend. The reef runs from a snorkeller-friendly 5 metres down to 36 metres, putting serious depth on the table for those who want it. Visibility typically ranges from 15 to 30 metres, so you can watch the action from a distance before committing. Current stays mild, which helps. Look carefully into the gorgonian fans for pygmy seahorses, and keep an eye on the sandy margins for marbled stingray and sea snakes. Whitetip and gray reef sharks work the deeper sections regularly. Watch for jellyfish throughout the water column and stay aware of boat traffic on ascent.
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The deeper sections below 25 metres are where the shark activity tends to concentrate, so plan a slow descent along the reef wall rather than dropping straight to the bottom and burning your bottom time. Make sure your surface marker buoy is ready before you ascend given the boat traffic.
The site is located on the outer Great Barrier Reef and is accessible only via a full-day boat trip or liveaboard, primarily departing from Port Douglas. Operators like Divers Den and Mike Ball Dive Expeditions are known to visit this site.
The marine stinger (jellyfish) season runs from approximately November to May. Wearing a full-body wetsuit or stinger suit is highly recommended during these months.
Depth
5-36m
Visibility
15-30m
Skill Level
Intermediate
Entry
Boat
Boat required
Water Temp
22-29°C
Current
Mild
Typical Dive
50 min
Best Time
Jan, Feb, Mar, Apr, May, May, Jun, Jun, Jul, Jul, Aug, Aug, Sep, Sep, Oct, Oct, Nov, Dec
Crack a Jack in Queensland requires an Advanced Open Water certification as a minimum. The site reaches depths between 5 and 36 metres, with sections demanding intermediate dive skills and experience managing mild currents. Divers must book through licensed boat charters operating from Cairns or Port Douglas.
Crack a Jack ranges from 5 metres at the shallowest sections to 36 metres at maximum depth. The varied depth profile allows divers to explore different reef zones, though the deeper areas require Advanced certification. Visibility typically ranges between 15 and 30 metres throughout the site.
Crack a Jack near Cairns is known for pygmy seahorses on gorgonian fans, marbled stingrays, and schooling jacks. Divers regularly encounter whitetip reef sharks, sea snakes, fusiliers, and glass fish sheltering in the reef structure. The site's varied depths support diverse species from small macro subjects to larger pelagics.
The optimal months for diving Crack a Jack are May through July and November through December. Water temperatures during these periods range between 22 and 29 degrees Celsius with visibility between 15 and 30 metres. Conditions remain diveable year-round, though these months offer the most consistent underwater visibility.
Night diving is available at Crack a Jack through charter operators from Cairns and Port Douglas. The site transforms after dark with nocturnal species emerging, though divers must hold Advanced Open Water certification and be comfortable with the 5 to 36 metre depth range. Charter boats provide guided night dive services with appropriate lighting and safety equipment.
Crack a Jack is accessed exclusively by boat from Cairns or Port Douglas in Queensland. Charter operators provide guided tours with full facilities including equipment rental, dive shops, and cafés at departure points. No entry fee applies to the site itself, though charter costs vary by operator and trip duration.
Primary hazards at Crack a Jack include jellyfish, boat traffic, and marine life interactions with sea snakes and sharks. The site's depth to 36 metres and mild to strong currents require proper buoyancy control and dive planning. Divers should maintain safe distances from whitetip reef sharks and avoid touching gorgonian fans where pygmy seahorses reside.
Crack a Jack is not suitable for beginners as it requires Advanced Open Water certification and intermediate skills. The depths reaching 36 metres, combined with mild currents and potential marine life encounters, exceed Open Water diver training limits. Newly certified Advanced divers should dive with experienced guides from Cairns charter operators.
Yes, equipment rental is available at or near Crack a Jack in Cairns and Port Douglas. Contact local dive operators for specific gear availability and prices.
A 3mm wetsuit is recommended for diving at Crack a Jack in Cairns and Port Douglas. Water temperatures range from 22°C to 29°C.