Top 10

Sure, we’ve got killer white sharks and deadly box jel­ly­fish, but Aus­tralia’s wa­ters boast many more dan­ger­ous ma­rine crea­tures that aren’t so well known. Here are 10 of them.

Australian Geographic - - Contents -

MOST BEACH­GO­ERS and ocean users around Aus­tralia give thought, be­fore en­ter­ing the wa­ter, to sharks, jel­ly­fish and croc­o­diles. But you might want to also con­sider the lesser-known ma­rine crea­tures that can de­liver nasty bites and stings.While not as no­to­ri­ous as our head­line-grab­bing biters and toxic avengers, many other aquatic species come equipped with weapons that can cause se­vere in­jury and, oc­ca­sion­ally, death.


Of the 80 species of cone shell in Aus­tralian wa­ters, a hand­ful are po­ten­tially lethal to hu­mans. Th­ese preda­tory sea snails have a har­poon-like tooth that in­jects a fast-act­ing venom. Se­ri­ous en­ven­o­ma­tion causes in­tense pain and swelling at the st­ing site, numb­ness, tin­gling, nau­sea and vom­it­ing. Seek med­i­cal at­ten­tion im­me­di­ately.


Two stonefish species oc­cur in Aus­tralia, mainly in the trop­ics. Their venom is among the most po­tent of any fish and can be fa­tal. Ex­cel­lently cam­ou­flaged, th­ese am­bush preda­tors grow to about 35cm and rarely swim away if dis­turbed. In­stead, they erect ven­omous dor­sal spines that can be strong enough to pierce rub­ber-soled shoes. Seek med­i­cal at­ten­tion im­me­di­ately.


The largest and bright­est oc­cur in coastal trop­i­cal wa­ters where they at­tach to rocks or reefs, wav­ing ven­omous ten­ta­cles in the cur­rent to snare pass­ing prey. For hu­mans, brushes with some species pro­duce sim­i­lar symp­toms to jel­ly­fish stings.


Th­ese colo­nial an­i­mals are hy­dro­zoans; they are re­lated to, but are not, true corals. Highly vari­able in size, shape and colour, all have a hard skele­ton with tiny pores from which they pro­trude ten­ta­cles armed with sting­ing cells. Th­ese stun prey and can cause divers and snorkellers in trop­i­cal wa­ters in­tense pain if they brush against them. How­ever, they’re not par­tic­u­larly toxic.


Some sponge species have de­vel­oped tox­ins and tiny, sharp spines as de­fences. Th­ese can cause skin ir­ri­ta­tion if touched, with symp­toms in­clud­ing red­ness, prick­ling, itch­ing and tiny blis­ters, which can de­velop later into burn­ing and pain. Symp­toms may worsen over 24 or more hours and the area can take a week or more to re­turn to nor­mal. But sponges are not very toxic.


Th­ese fern-like colo­nial an­i­mals grow on sub­merged rocks or reefs, of­ten where there is a cur­rent that car­ries plank­ton prey past their ‘fronds’, which are lined with sting­ing polyps. Even a brush against a sting­ing hydroid can pro­duce pain. The ef­fects seem vari­able, rang­ing from no re­ac­tion to in­tense pain and weals that can take weeks to heal.


Th­ese are com­mon and wide­spread, and have stiff pro­trud­ing bris­tles which can in­jure skin on con­tact. In some species, in­clud­ing fire­worms, the bris­tles are ven­omous. They break off eas­ily in skin and are hard to see; a rash is of­ten the only sign. Symp­toms, in­clud­ing itch­ing, burn­ing, pain and swelling, are usu­ally worse in the first few days but can last up to 10 days.


Lion­fish are Aus­tralia’s best-known scor­pi­onfish. They grow up to 35cm, usu­ally have stripes and feath­ery fins, and are of­ten seen in trop­i­cal and sub­trop­i­cal wa­ters. They can be ag­gres­sive, and have ven­omous spines that cause ex­tremely painful stings. This isn’t nor­mally fa­tal, but symp­toms can in­clude headaches, vom­it­ing, seizures, paral­y­sis and breath­ing dif­fi­cul­ties.


Sea urchins oc­cur in a va­ri­ety of sizes and colours with spines that range from stubby and blunt to long and sharp. Some are ven­omous. Long-spined species cause the most com­mon prob­lem: a spine break­ing off in a vic­tim’s skin, which can cause in­fec­tion. The spines of some species dis­ap­pear in a few days; oth­ers have spines that can stay un­der the skin for months and emerge some dis­tance from the orig­i­nal wound. The punc­tures are painful.


Many fish have sharp spines that can cause punc­ture wounds. In the old wife (the some­what deroga­tory name comes from the grumbling sound the fish makes when taken from the wa­ter), dor­sal spines con­tain venom known to cause pain. They oc­cur in shel­tered habi­tats such as sea­grass beds, wharfs, jet­ties and coastal reefs.

PHOTO CRED­ITS: 1. TEX­TILE CONE SNAIL ( Conus tex­tile), GETTY; 2. REEF STONEFISH ( Sy­nan­ceia ver­ru­cosa), GARY BELL/OCEANWIDE IM­AGES; 3. ANEMONE ( Actin­oden­dron sp.), GE­OR­GETTE DOUWMA/ NATURE PIC­TURE LI­BRARY; 4. FIRE CO­RAL ( Mille­pora platy­phylla), GARY...

Want to know more? Check out our new book Aus­tralia’s Most Dan­ger­ous, a con­cise, ac­ces­si­ble field guide to our re­mark­able but of­ten dan­ger­ous snakes, spi­ders and ma­rine crea­tures. On sale now, it in­cludes up-to­date first aid ad­vice. Head to...

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