In hot water: coral bleaching sparks fears over Lord Howe reefs - Sydney Morning Herald

The Portuguese man-o'-war or bluebottle (Physalia physalus), is well known throughout Australian waters (and both the Pacific and Atlantic oceans) for causing painful stings. No fatalities have been confirmed in Australia. The float, or 'body' measures 2-15 cm, while the main or fishing tentacle may be up to 10m long. This tentacle is responsible for most of the stings. The larger Atlantic specimens probably represent more of a threat to human life. Its venom contains lethal and haemolytic components and has been shown to produce nerve conduction disturbances, flaccid paralysis and smooth muscle contraction in experimental animals. In human envenomation, pain is the most prominent feature, along with localized skin lesions with a "string of beads" appearance; discrete weals surrounded by erythema. Systemic symptoms are uncommon but may include headache, nausea and vomiting, abdominal pain and occasionally collapse. First aid consists of removal of the tentacles, preferably with forceps. Vinegar is not recommended. Analgesia may be required, although most stings respond to ice packs and/or topical anaesthetic agents