Crocodiles

Around the northern Australian coastline, saltwater crocodiles (salties) are a real danger. They also inhabit estuaries, creeks and rivers, sometimes a long way inland. Observe safety signs or ask locals whether that inviting-looking waterhole or river is croc free before plunging in.

Jellyfish

With venomous tentacles up to 3m long, box jellyfish (aka sea wasps or stingers) inhabit Australia's tropical waters. They're most common during the wet season (October to March) when you should stay out of the sea in many places. Stinger nets are in place at some beaches, but never swim unless you've checked. 'Stinger suits' (full-body Lycra swimsuits) prevent stinging, as do wetsuits. If you are stung, wash the skin with vinegar then get to a hospital.

The box jellyfish also has a tiny, lethal relative called an irukandji, though to date, only two north-coast deaths have been directly attributed to it.

Sharks

Despite extensive media coverage, the risk of shark attack in Australia is no greater than in other countries with extensive coastlines. Check with surf life-saving groups about local risks.

Snakes

Australia has plenty of venomous snakes. Most common are brown and tiger snakes, but few species are aggressive. Unless you're poking a stick at or accidentally standing on one, it's extremely unlikely that you'll get bitten. If you are bitten, prevent the spread of venom by applying pressure to the wound and immobilising the area with a splint or sling. Stay put and get someone else to go for help.

Spiders

Australia has several poisonous spiders, bites from which are usually treatable with antivenenes. The deadly funnel-web spider lives in New South Wales (NSW; including Sydney); bites are treated as per snake bites (pressure and immobilisation before transferring to a hospital). Redback spiders live throughout Australia; bites cause pain, sweating and nausea. Apply ice or cold packs, then transfer to hospital. White-tailed-spider bites may cause an ulcer that's slow and difficult to heal. Clean the wound and seek medical assistance. The disturbingly large huntsman spider is harmless, though seeing one can affect your blood pressure and/or underpants.

At the Beach

Check surf conditions and be aware of your own expertise and limitations before entering the waves. Patrolled, safe-swimming areas are indicated by red-and-yellow flags – swim between them. Undertows (rips) are a problem: if you find yourself being carried out to sea, swim parallel to the shore until you're out of the rip, then head for the beach.

Several people are paralysed every year by diving into shallow waves and hitting sand bars: look before you leap.

Always use SPF30+ sunscreen; apply it 30 minutes before going into the sun and repeat applications regularly.

Bushfires

Bushfires happen yearly across Australia. In hot, dry and windy weather, and on total-fire-ban days, be extremely careful with naked flames (including cigarette butts) and don't use camping stoves, campfires or BBQs. Bushwalkers should delay trips until things cool down. If you're out in the bush and you see smoke, take it seriously: find the nearest open space (downhill if possible). Forested ridges are dangerous places to be.

Cold Weather

More bushwalkers in Australia die of cold than in bushfires. Even in summer, particularly in highland Tasmania, Victoria and NSW, conditions can change quickly, with temperatures dropping below freezing and blizzards blowing in. Hypothermia is a real risk. Early signs include the inability to perform fine movements (eg doing up buttons), shivering and a bad case of the 'umbles' (fumbles, mumbles, grumbles, stumbles). Get out of the cold, change out of wet clothing and into dry stuff, and eat and drink to warm up.

Heat Exhaustion

Symptoms of heat exhaustion include dizziness, fainting, fatigue, nausea or vomiting. Skin becomes pale, cool and clammy. Treatment consists of rest in a cool, shady place and fluid replacement with water or diluted sports drinks.

Heatstroke is a severe form of heat illness and is a true medical emergency, with heating of the brain leading to disorientation, hallucinations and seizures. Prevent heatstroke by maintaining adequate fluid intake, especially during physical exertion.

Crime

Australia is a relatively safe place to visit, but you should still take reasonable precautions. Avoid walking around alone at night, don't leave hotel rooms or cars unlocked, and don't leave valuables visible through car windows.

Some pubs in Sydney and other big cities post warnings about drugged or 'spiked' drinks: play it safe if someone offers you a drink in a bar.

Dengue Fever

Dengue fever occurs in northern Queensland, particularly during the wet season. Causing severe muscular aches, it's a viral disease spread by a day-feeding species of mosquito. Most people recover in a few days, but more severe forms of the disease can occur.

Giardiasis

Giardia is widespread in Australian waterways. Drinking untreated water from streams and lakes is not recommended. Use water filters, and boil or treat this water with iodine to help prevent giardiasis. Symptoms consist of intermittent diarrhoea, abdominal bloating and wind. Effective treatment is available (tinidazole or metronidazole).

Ross River Fever

The Ross River virus is widespread in Australia, transmitted by marsh-dwelling mosquitoes. In addition to fever, it causes headache, joint and muscular pain, and a rash that resolves after five to seven days.

Tick Typhus

Predominantly occurring in Queensland and NSW, tick typhus involves a dark area forming around a tick bite, followed by a rash, fever, headache and lymph-node inflammation. The disease is treatable with antibiotics (doxycycline).

Viral Encephalitis

This mosquito-borne disease is most common in northern Australia (especially during the wet season), but poses minimal risk to travellers. Symptoms include headache, muscle pain and sensitivity to light. Residual neurological damage can occur and no specific treatment is available.