Agincourt Reef

Overview & Topography

Agincourt Reef is one of the premier dive sites in the Cairns region, characterized by a depth profile spanning 5–22m with a maximum bottom depth of 22 metres. Access is typically conducted via Boat / Liveaboard Entry, experiencing mild to moderate (tidal shifts) current conditions.

The underwater landscape presents a dynamic blend of high-profile reef structures, sand channels, and dramatic drop-offs that support high biodiversity and clear waters.

Detailed Dive Route & Navigation Plan

1. Entry & Descent Phase (Surface to 12m)

• Descent Strategy: Following the pre-dive briefing, divers execute a controlled descent via the vessel mooring line or a negative back-roll to prevent surface drift.
• Equalization Protocol: Equalize early and often (every 1 metre) within the first 10 metres of the water column to protect eardrums against rapid pressure increases.
• Initial Orientation: Settle neutrally above the sandy substrate at 10m. Set your compass heading and confirm buddy positioning before proceeding towards the main reef structure.

2. Deep Section & Exploration (14m to 22m)

• The Main Reef & Drop-Off: Follow the natural contours of the reef, keeping the main coral wall or rock structure on your left/right shoulder as dictated by the current.
• Key Geological Features: Explore the deep swim-throughs, overhangs, and coral bommies that characterize Agincourt Reef. Keep an eye on your dive computer: as you reach depths of 22m, your No-Decompression Limit (NDL) will reduce rapidly.
• Turnaround Pressure: Initiate the return leg or ascend to shallower depths when the first buddy in the team reaches 110 bar (or one-third of total cylinder capacity).

3. Shallow Progression & 5m Safety Stop

• Gradual Ascent: Ascend slowly along the reef crest at a rate no faster than 9–10 metres per minute.
• The Safety Stop: Conduct a mandatory 3-to-5-minute safety stop at 5 metres (15 feet) in calm water or along the mooring line before completing a 360-degree surface scan and surfacing with a deployed Surface Marker Buoy (SMB).

Marine Life & Habitat Zones (Biologically Verified)

• Apex & Pelagic Predators: Giant Potato Cod (Epinephelus tukula), Humphead / Maori Wrasse (Cheilinus undulatus), Grey Reef Sharks (Carcharhinus amblyrhynchos).
• Reef Fish & Keystone Species: Giant Clams (Tridacna gigas), Clown Anemonefish (Amphiprion ocellaris), Coral Trout (Plectropomus leopardus).
• Macro Biodiversity & Benthic Invertebrates: Mantis Shrimp (Odontodactylus scyllarus), Flame File Shells (Limaria fragilis), Leaf Scorpionfish (Taenianotus triacanthus).
• Elasmobranchs & Marine Reptiles: Whitetip Reef Sharks, Green Sea Turtles, Hawksbill Turtles, Seasonal Dwarf Minke Whales (Balaenoptera acutorostrata).

Gas Management & Diver Safety (The Craig Rule)

• Mandatory Certification Level: Open Water (18m). Divers certified to Open Water level (18m limit) must strictly remain on the upper reef plateau and MUST NOT descend past 18m without an instructor or Advanced Open Water certification.
• Gas Planning: Standard 12-litre (80 cu ft) aluminum or steel cylinders filled with Air (21% O2) or Enriched Air (Nitrox 32%). On Nitrox 32%, the Maximum Operating Depth (MOD) is 33.8m at a maximum PPO2 of 1.4 bar.
• Emergency Protocols: In the event of buddy separation, search for 1 minute while hovering in place, then ascend safely at 9m/min to reunite at the surface.