418 Dive Log Australasia JUNE 2026.pdf

significant as it is visually breathtaking. No other place on Earth hosts such a dense, predictable aggregation of Giant Australian Cuttlefish in such accessible conditions. Stony Point is more than just a South Australian highlight—it’s a globally recognised natural event. The ease of access, combined with the reliability of the spectacle, draws marine scientists, filmmakers, and ocean enthusiasts from around the world to observe the phenomenon—often just metres from shore. Stony Point is widely considered one of the safest and most beginner-friendly snorkelling spots on this coastline. It’s tucked into False Bay, where the conditions are usually calm and the currents mild. Northerly (off shore) winds tend to bring the best surface condition. Visibility typically ranges between three to five metres in winter. The bottom gradually slopes away from shore, reaching depths of around seven metres some 100 metres out—but there’s rarely a reason to swim that far. Most of the action takes place within just a few metres off the shoreline. The rocky seabed in the shallows makes it easy to spot cuttlefish, whereas further out, increased seagrass and algae cover can obscure them, especially given their remarkable camouflage. Staying close to shore not only improves your chances of seeing them up close. As soon as you dip your head below the surface, you’re likely to find yourself surrounded by these spectacular creatures. The best viewing times are between 10 am and 3 pm, when the animals are most active. Even with gentle conditions, the water remains cold—usually between 14 and 17 °C—so a good-quality at least 5mm open cell wetsuit is essential. There are no lifeguards or rangers on site, so it’s important to snorkel with a buddy and follow standard safety precautions. For those properly prepared, Stony Point offers one of the most accessible and awe inspiring marine wildlife encounters in the country. What makes Stony Point the chosen breeding ground? The answer lies in the unique habitat. The upper Spencer Gulf is predominantly sand and mud, which offers few secure surfaces for eggs. In contrast, Stony Point features a shallow fringing reef spanning 10 km, made up of ledges, caves, and ancient sandstone slabs. These natural features create an underwater nursery, offering protection and anchoring points for egg-laying females. It has abundant, solid rocky surfaces, which is why the entire Spencer Gulf population converges here. The reef’s west-to-east orientation and strong currents help maintain water flow and oxygenation, while the Gulf’s cool waters—colder than surrounding seas due to its inverse estuary conditions— provide the perfect temperature for egg incubation. The migration begins as water temperatures dip below

17 °C—one of the key environmental triggers that signals the start of the breeding season. The first individuals arrive in mid to late May, and by early June, the spawning grounds are teeming with life. The timing ensures that fertilised eggs will develop through the coldest months of the year, which provides optimal conditions for their survival. By early June, thousands of cuttlefish converge en masse across the rocky inshore reefs surrounding Point Lowly, Fitzgerald Bay, False Bay, and Black Point. This area, now protected as the Cuttlefish Coast Sanctuary Zone and recognised on Australia’s National Heritage register, offers the ideal mix of habitat, depth, and structure for their complex reproductive rituals. Normally solitary creatures, these marine invertebrates transform the shallows into a dynamic stage for one of the most visually arresting displays in the animal kingdom. Males compete fiercely for mates, flashing through a kaleidoscope of shifting hues and textures, hoping to outshine their rivals and impress the females. It’s a hypnotic, high-stakes ballet of concealment, imitation, and ritual—all for the sake of reproduction and the continuation of the species. Though often mistaken for fish, Giant Cuttlefish are actually close kin to octopuses and squid. Their biology is fascinating: they possess three hearts, circulate copper based blue blood, and wield eight arms along with a pair of extendable feeding tentacles. Their W-shaped pupils allow simultaneous forward and backward vision and while they cannot perceive colour, they excel at producing it. Thanks to millions of specialised skin cells known as chromatophores, iridophores, and leucophores, cuttlefish can rapidly shift their colour, texture, and even body shape. These abilities are vital for camouflage, signalling intentions, and above all, during courtship. Males perform dazzling displays of pulsing stripes and shifting colours to lure females and intimidate competitors. Their skin also features papillae—tiny muscular structures that can protrude or flatten to alter their appearance further. Males outnumber females by a significant margin, often as high as 8 to 1, resulting in fierce competition. Large males dominate, using vibrant hue displays and physical guarding to secure access to females. These confrontations can be brutal, leaving males with torn tentacles or visible scars. Scan the rocky seabed carefully and you may see a large male lying low against the substrate. He’s not idle—he’s vigilantly protecting a nearby female, possibly while she deposits eggs under a ledge. Rival males circle at a distance, waiting for any lapse in attention. The instant he shifts focus, one of them will make a quick attempt to dash in and claim a mating opportunity.

A male and female Giant Cuttlefish embrace in a delicate, head-to-head mating posture

Clash of the giants - an intense visual duel for dominance and a chance to mate

27

Dive Log Australasia #418 June ‘26

www.divelog.net.au