Underwater on the Peninsula
The Mornington Peninsula’s underwater world is unexpectedly rich — the convergence of Port Phillip Bay’s sheltered waters and Bass Strait’s cooler currents creates a marine environment that supports weedy seadragons (the region’s signature marine species — a relative of the seahorse, endemic to southern Australian waters, and notoriously difficult to spot), Australian fur seals (curious and playful when encountered underwater), and the kelp forests, sponge gardens, and reef systems that line the peninsula’s coastline.
Snorkelling and swimming tours take visitors to the best sites for encountering this marine life — either from the shore (guided snorkel walks at sites like Rye Pier, Flinders Pier, and Portsea) or by boat (to the seal colonies and offshore reefs). The weedy seadragon snorkels are the specialist offering — guided by marine naturalists who know the specific sites where the seadragons shelter in the seagrass beds, and who can spot the extraordinarily well-camouflaged animals that most unguided snorkellers swim straight past.
Weedy seadragons — these extraordinary creatures (up to 45 cm long, leafy appendages, near-perfect camouflage) live in the seagrass beds and kelp forests along the peninsula’s coastline. The guided snorkel experience is typically the only reliable way to see them — the guides know the specific patches of seagrass where the seadragons reside and can point them out to snorkellers.
Seal snorkelling — swimming with Australian fur seals at their haul-out sites is one of the peninsula’s most memorable marine experiences. The young seals are inquisitive and acrobatic in the water, often approaching snorkellers and playing around them.
Frequently Asked Questions
Do I need snorkelling experience?
No prior experience is required for most guided snorkelling tours — the guides provide equipment and instruction, and the sites are typically sheltered with calm conditions. Basic swimming confidence is sufficient.
When is the best time for snorkelling?
Summer and autumn (December–May) for the warmest water temperatures and the calmest conditions. Weedy seadragons are present year-round. Seals are reliably present at the haul-out sites throughout the year.
What will I see underwater?
Weedy seadragons, Australian fur seals (on seal-specific tours), kelp forests, sponge gardens, reef fish, octopus, cuttlefish, and — in season — various ray species in the sandy shallows.