Meet the site
Stonehenge on Agincourt Reef No. 3 is one of the most highly regarded coral sites out of Port Douglas. Silverseries describes it as rich in coral diversity with awesome swim-throughs, and Scuba IQ goes further, calling it one of the most incredible sites on the Great Barrier Reef, absolutely loaded with healthy coral. The name comes from the standing coral pillars and arches that give the reef its structure. Big coral heads have grown up from the sand to around 5 m below the surface, and in places they have joined overhead to form a sequence of arches and short tunnels. Swimming through them is the highlight of the dive – they are open, lit from the sides and short enough to suit any diver with good buoyancy control. Inside, the walls are lined with sponges, soft corals and small fish sheltering from the light. Around and between the pillars the coral cover is dense and varied: staghorn and plate Acropora, massive boulder corals, brain corals, soft corals and sea whips. The fish life matches it. Fusiliers swirl overhead, clownfish nestle in anemones on the tops of pillars, and cuttlefish hover near coral heads. Giant clams are dotted across the reef, and reef sharks are often seen cruising the sand edges. The maximum depth is around 20 m, but most of the dive takes place between 8 and 15 m, which keeps it suitable for new open water divers and leaves plenty of light for photography. Scuba IQ notes it appeals to a wide range of diver abilities. Stonehenge is a site to take slowly. Rather than covering distance, spend time weaving through the swim-throughs and examining the coral surfaces, where nudibranchs, flatworms and shrimps reward close inspection. It is one of the sites guides most often recommend when asked for the best coral on Agincourt.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Stonehenge (Agincourt Reef 3) is recorded as Reef in Port Douglas. The listed access is boat (day trip). Confirm the actual meeting point, route and permission to visit; a map pin does not establish any of these.
Topics flagged by the stored research
These are questions prompted by the existing notes, not a verified or complete hazard assessment.
- Other water users
- Ask about vessel activity, exclusion areas and the agreed surface arrangements.
- Overhead environments
- Ask whether the plan stays entirely in open water. A wreck or cave listing is not permission or training to enter.
Historical access notes exist for this record, but have not been independently verified for current use. Request current directions from the operator or site manager rather than following an old entry description.
Questions, answered
Is Stonehenge (Agincourt Reef 3) suitable for my certification?
The record lists Advanced Open Water. That does not establish suitability for every route or day. Share your training, recent experience and equipment needs with the operator and ask about the specific proposed dive.
Can I book Stonehenge (Agincourt Reef 3) through YouDive?
YouDive is an independent research directory. Contact an operator directly to confirm whether it currently runs the trip, the inclusions and the booking terms.
What you might see
Giant clams, clownfish in anemones, cuttlefish, fusiliers, reef sharks, nudibranchs, sponges, staghorn, plate, brain and soft corals
Location
A coral-rich reef on Agincourt Reef No. 3 with a series of swim-throughs.
Facilities nearby
Departs Crystalbrook Superyacht Marina, Wharf Street, Port Douglas – car parking, toilets, cafes and restaurants at the marina; dive shops in town for gear hire and air
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
silverseries.com.auposeidon-cruises.com.auscubaiq.com.auRecord updated 27 Sept 2026. Source claims are being reviewed.