Meet the site
Three Sisters is a pretty garden site on Agincourt Reef No. 4 built around three prominent bommies that sit about 50 m from the mooring. Silverseries and Poseidon note that it is often visited by juvenile grey reef whalers and that huge schools of fish congregate here. The three bommies rise from a sandy floor at up to 20 m to within a few metres of the surface, their walls covered in hard corals, sea fans and soft corals. Each attracts its own congregation of fish: fusiliers stream around the upper parts, red bass and spangled emperor patrol the bases, and schools of snapper and sweetlips hang in the shelter of the coral. The fish density is the standout feature – on a good day the water between the sisters is thick with life. Grey reef whalers, mostly juveniles, cruise between the bommies and along the sand, and whitetip reef sharks rest on the bottom. Stingrays lie in the sand channels, and turtles are regular visitors. Between and around the bommies is a garden reef of mixed hard corals, which is where snorkellers spend their time. The dive plan is simple and satisfying: swim out to the bommies, visit each in turn and return over the garden reef. The distance from the mooring is short enough that no one gets lost, and the bommies make obvious landmarks. The site suits all levels, although divers should keep an eye on depth when circling the base of each sister. Visibility averages around 18 m and often reaches 30 m. Three Sisters is a reliable choice for a relaxed but fishy dive, and it is an excellent place for photographers to capture schools of fish framed by coral pinnacles. Do not confuse it with the Three Sisters at Michaelmas Reef, a Cairns site visited by Silverswift.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Three Sisters (Agincourt Reef 4) is recorded as Pinnacle/Bommie 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.
- Planned depth
- Confirm the intended route and training requirements; the recorded maximum is not a target.
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 Three Sisters (Agincourt Reef 4) 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 Three Sisters (Agincourt Reef 4) 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
Juvenile grey reef whalers, whitetip reef sharks, red bass, spangled emperor, fusiliers, snapper, sweetlips, stingrays, turtles, sea fans
Location
A garden site on Agincourt Reef No. 4 with three prominent bommies about 50 m from the mooring.
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.auRecord updated 27 Sept 2026. Source claims are being reviewed.