Victoria dive sites

The giant spider crab aggregation at Flinders Pier typically occurs from late May through July, with peak numbers usually in June. Thousands of spider crabs gather in the shallows around the pier to moult their shells, creating an extraordinary spectacle that has been featured in nature documentaries worldwide. The crabs pile up in layers several deep, sometimes covering the entire seafloor beneath the pier. The exact timing varies each year, and local dive shops monitor conditions and report when the aggregation begins.

Flinders Pier is widely considered one of the best night dive sites in Australia. After dark, the pier pylons come alive with creatures that are rarely seen during the day. Blue-ringed octopus emerge to hunt, their iridescent rings pulsing in torchlight. Cuttlefish hover beneath the pier. Seahorses that are nearly impossible to find in daylight become more visible on exposed surfaces. The resident weedy sea dragons take on a luminous quality under torch beams. Shore access and the shallow depth make night dives safe and easy to manage.

Flinders Pier is a shore dive with easy access from the beach beside the pier. Entry and exit are via a sandy beach, and the dive follows the pier pylons to a maximum depth of about 12 metres. A 7mm wetsuit or dry suit is recommended as water temperatures range from 11 degrees in winter to 21 degrees in summer. Visibility varies from 5 to 15 metres. There is limited parking near the pier, and on weekends during spider crab season it fills up early. Check tide times before diving, as incoming tides generally bring better visibility.

Weedy seadragons are reliably found at several Mornington Peninsula sites including Flinders Pier, Rye Pier, and Portsea Pier. They inhabit kelp and seagrass beds between 3 and 15 metres depth. Winter months (June to September) are particularly productive as males carry eggs and remain in predictable locations. Local dive operators know specific locations of resident individuals and can guide you directly to them.

Water temperatures at the Mornington Peninsula range from 11 degrees in winter to 21 degrees in summer. Most divers use a 7mm wetsuit with hood, gloves, and boots during summer, switching to drysuits during winter months. Some cold-tolerant divers use 5mm suits in summer, but for comfort during longer dives, heavier insulation is recommended year-round. The reward for the cold is uncrowded sites and unique temperate marine life.