and three hours. Even when a boat was on call it could take 45 minutes to respond. Boat availability soon became a problem with only five LCMs, leaving personnel waiting for one to arrive. The twelve smaller LCAs were also employed; although they could operate when the tides made waters too shallow for the pinnaces, their wooden bottoms were easily holed by coral outcrops. On 15 August, some men were transferred from Campania by one of its three Dragonfly helicopters, but the weather closed in and they could not be picked up again, having to find shelter on Tracker and Zeebrugge, which were moored in the lagoon. To get around these problems, tented camps were established for the scientists at H1 on Hermite Island and Cocoa Beach (also known as T2) on Trimouille Island. Scientific rehearsals were held on 12 and 13 September. This was followed by an operational rehearsal on 19 September, which included fully assembling the bomb, since the radioactive components had arrived the day before on a Sunderland. Penney arrived by air on 22 September. Everything was ready by 30 September, and the only remaining factor was the weather. This was unfavourable on 1 October but improved the following day, when Penney designated 3 October as the date for the test. The final countdown commenced at 07:45 local time on 3 October 1952. Plym was moored a few hundred meters west of T2 (approx 20°24'16"S, 115°34"E). The bomb was successfully detonated at 07:59:24 on 3 October 1952 local time, which was 23:59:24 on 2 October 1952 UTC, 00:59:24 on 3 October in London, and 07:59:24 on 3 October in Perth. The explosion occurred below the water line, and left a saucer-shaped crater on the seabed deep and across. The yield was estimated at . All that was left of Plym was a "gluey black substance" that washed up on the shore of Trimouille Island. Derek Hickman, a Royal Engineer observing the blast aboard Zeebrugge, later said of Plym, "all that was left of her were a few fist-sized pieces of metal that fell like rain, and the shape of the frigate scorched on the sea bed." The bomb had performed exactly as expected. Two Dragonfly helicopters flew in to gather a sample of contaminated seawater from the lagoon. Scientists in gas masks and protective gear visited points in pinnaces to collect samples and retrieve recordings. Tracker controlled