Marine poisons are introduced by variety of mechanisms:

• Puncture injury from a spine: stingray, catfish, scorpion fish, weever fish, lion fish and sea urchins.
• Stinging by a specialised apparatus (nematocyst): jellyfish, corals and sea anemones.
• Bites that inject venom from a specialised apparatus: blue-ringed octopus, sea snake and cone shell.
• Poisoning by ingestion of toxic seafood: ciguatera, paralytic shellfish poisoning, puffer fish poisoning and scombroid fish poisoning.

The main species that cause marine envenomation belong to one of five phyla:

Invertebrates that have tentacles equipped with nematocysts that discharge toxins on contact.

Four classes are poisonous:

Blue bottle, Physalia utriculus
Pacific man-o’war, Physalia physalis
Hydroid corals, eg Millepora alcicornus, the stinging fire coral

Box jellyfish, Chironex fleckeri
Quaddie, Chiropsalmus quadrigatus
Irukandji jellyfish, Carukia barnesi
Jimble, Carybdea rastoni
Morton Bay stinger (Fire Jelly), Tamoya spp.

Rhyzostomaspp.
Sea nettle Chrysaora spp.
Hair jelly (Hairy Stinger), Cyanea spp.
Blubber jellyfish, Catostylus spp.
Little mauve stinger, Pelagia noctiluca

Hard corals, Order Scleractinia: Only some species have stinging nematocysts capable of harming people. More common is mechanical injury and infections from contact with hard corals.
Soft corals, Order Alcyonaea
Sea anemones, Order Actiniaria
Tube anemones, Order Ceriantharia

Blue-ringed octopuses, Hapalochlaena maculosa, H. fasciata, H. lunulata plus three other unnamed species.
Cone shells, Conus spp.

2.3.5.2.3.1 Crown-of-thorns starfish, Acanthaster planci

2.3.5.2.3.2 Sea urchins, Class Echinoidea
Black (Long-spined) Sea Urchin, Diadema setosum
Flower Sea Urchin, Toxopneustes pileolus

2.3.5.2.4.1 Venomous fish
Stonefish Synanceia spp.
Scorpionfish, Family Scorpaenidae, eg the Lionfish (Butterfly Cod) Pterois volitans
Family Synanceiidae, eg the Goblinfish Glyptauchen panduratus
Surgeonfish, Family Acanthurus
Catfish, Families Ariidae and Plotosidae

2.3.5.2.4.2 Stingrays
Southern Eagle Ray, Myiobatis australis
White-spotted Eagle Ray, Aetobatus narinari
Black Stingray Dasyatis thetidis
Blue-spotted Maskray Dasyatis kuhlii

2.3.5.2.4.3 Sea snakes, Family Hydrophiidae
eg, Beaked sea snake, Enhydrina schistosa

Stinging Sponges, Class Demospongiae

Jellyfish venoms are not well identified. The following toxins have been isolated: histamine, serotonin, dopamine, elastase, hemagglutinin, protease, collagenase and palytoxins. Chironex fleckeri venom causes skin necrosis, cardiac depression, respiratory depression, and anaphylaxis. Irukandji venom causes catecholamine release that may be responsible for some of the symptoms of envenomation. Anemone venoms contain neurotoxins, cardiotoxins, hemolysins and protease inhibitors.

Venom from the crown-of-thorns starfish contains saponins and haemorrhagins. Sea urchin venom is thought to contain proteins, steroid glycosides and inflammatory mediators.

Blue-ringed octopus venom contains tetrodotoxin; this inhibits the fast sodium channel, causing failure of nerve conduction and paralysis. Conopeptides from cone shells block sodium, potassium, and calcium channels, delay inactivation of sodium channels, and inhibit nicotinic and NMDA-glutamate receptors.

Catfish and Stingray venom contains vasoconstrictors. Stonefish venom contains proteins that have myotoxic, neurotoxic, and myocardial effects. Sea snake venom contains post-synaptic neurotoxins and myotoxins.

Commonwealth Serum Laboratories produced a sheep-derived Chironex fleckeri antivenom, a horse-derived Australian Stonefish antivenom and a Sea snake antivenom produced from horse antiserum against Sea snake (E. schistosa)