Marine life

Port Jackson Shark

Heterodontus portusjacksoni

A small, harmless, harness-marked shark that gathers in southern NSW winters to breed.

Port Jackson sharks are small, blunt-headed bottom sharks with a dark harness-shaped marking across the head and shoulders, and they are one of the great pleasures of a Sydney winter dive.

Through the cooler months they gather on inshore reefs in numbers, sometimes stacked several deep under a single ledge, to breed and lay their distinctive spiral-flanged egg cases wedged into rock crevices.

They are entirely harmless, crushing molluscs and urchins with flattened rear teeth, and they tolerate divers at close range. For a Sydney diver, their arrival is the compensation for water dropping below 17°C.

An editorial illustration of the breadth of Australian diving.

Scientific name	Heterodontus portusjacksoni
Typical size	Commonly 0.8–1.4 m
Peak months	June, July, August
Documented sites	6
States	New South Wales

When to see them

possible good peak

A winter visitor to NSW inshore reefs, aggregating to breed roughly May to September before dispersing south.

Where they are

Documented sites for Port Jackson Shark. Hover a marker for the site name.

Identification

blunt, rounded head with a pig-like snout
dark harness marking across the head and along the flanks
a spine in front of each dorsal fin
typically resting under ledges or on sand

Behaviour

Nocturnal feeder on molluscs, crustaceans and urchins.
Aggregates in winter to breed, often in the same locations year after year.
Lays a distinctive spiral egg case, wedged into rock crevices.

In-water etiquette

How divers behave around this species affects both the animal and everyone else's encounter.

Do not handle or move animals to photograph them.
Leave egg cases exactly where they are — they are wedged deliberately.
Take care not to crowd resting aggregations under ledges.

Where to see them

Sites where this species is documented as a reliable encounter.

Bare IslandSydney's most-dived shore site — weedy seadragons, extraordinary macro life and multiple routes.Gordons BayAn Eastern Suburbs shore dive with a long-established underwater nature trail.KurnellA cluster of Botany Bay shore dives including The Steps and The Leap, with wall terrain.Bass PointA rocky headland south of Wollongong with several entries and a protected reserve area.Terrigal HavenA sheltered Central Coast shore entry used heavily for training and night diving.Jervis Bay WallsTemperate sponge-covered walls and drop-offs in some of the clearest water in NSW.

Operators servicing those sites

Businesses documented as diving the sites above. Confirm seasonality and requirements directly.

Abyss Scuba DivingA Sydney operation associated with training across recreational and technical levels, boat diving and equipment services.Dive Centre BondiAn Eastern Suburbs operation providing recreational training, local diving and technical pathways.Shellharbour ScubaA Shellharbour operation serving the Illawarra diving community, with access to Bass Point and local reef diving.Central Coast DiversA Central Coast operation serving the local diving community with training and equipment support.Terrigal Dive CentreA Terrigal business combining training, equipment support and access to local reef and wreck diving.

Often seen on the same dives

Australian & New Zealand Fur SealsFast, acrobatic and endlessly curious — the highlight of Montague Island, Jervis Bay and Port Phillip.Eastern Blue GroperNew South Wales' state fish — large, inquisitive and often the first thing to greet a Sydney shore diver.Giant Australian CuttlefishThe world's largest cuttlefish, gathering in tens of thousands at Whyalla each winter.NudibranchsSea slugs of absurd colour and variety — the reason temperate Australian macro diving has a global reputation.Weedy SeadragonThe leafy's more widespread cousin — the signature animal of Sydney and Victorian shore diving.WobbegongCarpet sharks so well camouflaged that most divers swim straight past them — and occasionally put a hand on one.

Frequently asked questions

When do Port Jackson sharks appear in Sydney?

Broadly May to September, when they aggregate on inshore reefs to breed before dispersing south for summer.

Are they dangerous?

No. They are small, placid bottom-feeders that crush shellfish and pose no threat to divers.

Last researched: September 2026. Dive businesses change frequently — confirm current services, prices and requirements directly with the operator before booking.