Meet the site
HMS Plym (listed by Image Dive as HMAS Plym, about 1,300 tonnes) was the River-class frigate that carried Britain's first atomic device, detonated inside the ship off Trimouille Island on 3 October 1952 in Operation Hurricane. The vessel was destroyed and little remains beyond fragments on the seabed; Image Dive lists the site at about 12 m.
It is one of the strangest dive sites in Australia — less a wreck than a historic location — and should only be visited with local knowledge and awareness of radiation advice for the adjacent islands.
About the Montebellos: the group of more than 200 small limestone islands and islets lies 120 km west of Dampier and is protected as the Montebello Islands Marine Park, with more than 150 hard coral species, over 450 fish species, 170 echinoderms and 630 molluscs recorded. Flatback, green and hawksbill turtles nest here, and humpback, minke and Bryde's whales, dolphins and dugong frequent the waters. The islands carry a unique history: British atomic tests were conducted on and near Trimouille and Alpha islands in 1952 (Operation Hurricane) and 1956 (Operation Mosaic), and visitors are advised to visit rather than camp on those islands. Pearl farming has operated in the lagoons since the early 1900s.
Planning notes: Advanced Open Water certification is recommended and the site is rated advanced. Expect to spend most of the dive around 12 m, with a maximum of about 12 m. It can only be reached on a multi-day expedition or liveaboard, so it is usually one of several sites dived on the trip and choices are made by the crew on the day. Currents are significant, so timing around the tide is part of the plan. Best season: April–October. Traffic: remote/expedition only.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
HMAS Plym (Montebello Islands) is recorded as Wreck in Pilbara & Dampier. The listed access is boat (multi-day/liveaboard). 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.
- Current and timing
- Ask how the operator assesses the current window for the actual route. Historical tide notes are not a departure instruction.
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 HMAS Plym (Montebello Islands) 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 HMAS Plym (Montebello Islands) 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
Reef fish, corals recolonising the area
Location
Remains of the frigate HMS Plym, vaporised in the 1952 Operation Hurricane atomic test off Trimouille Island; site in about 12 m.
Facilities nearby
None – remote uninhabited islands. Radiation warning signs on Trimouille and Alpha islands.
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
imagedive.com.aumarinelife.org.auen.wikipedia.orgmontebello.com.auRecord updated 26 Sept 2026. Source claims are being reviewed.