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 this aspect, as it had the decontamination facilities. Air samples were collected by RAAF Avro Lincoln aircraft. Although the feared tidal surge had not occurred, radioactive contamination of the islands was widespread and severe. It was clear that had an atomic bomb exploded in a British port, it would have been a catastrophe worse than the bombing of Hiroshima and Nagasaki. The fallout cloud rose to and was blown out to sea, as intended; but later reversed direction and blew over the Australian mainland. Very low levels of radioactivity were detected as far away as Brisbane.