The Picnic Bay jetty was for decades the main arrival point on Magnetic Island, and though the ferries moved to Nelly Bay, the heritage-listed structure remains a popular fishing platform and a surprisingly productive jetty dive. The North Queensland Underwater Explorers Club documents it as a shore or boat dive with a maximum depth of about 6 m at the jetty head. Underwater the pylons are covered in soft corals, sponges, mussels and sea urchins, and the bottom is strewn with old metal straps from the jetty's construction and a fish-attracting device.

Life concentrates around the structure: schools of diamond fish, pike and sardines, sladey bream, lionfish, toadfish and juvenile coral trout, with lagoon rays and wobbegong sharks on the bottom. Cleaner shrimps and nudibranchs occupy the pylons. It is also stonefish country – the club reports specimens as large as an AFL football – so careful buoyancy is essential.

Visibility rarely exceeds 5 m, which gives the dive a muck-diving character rather than a reef feel, and it is at its best as a night dive, when crustaceans, cephalopods and hunting fish emerge. The club's equipment recommendations reflect the conditions: full wetsuit, booties, gloves, a torch, a glow stick on the tank valve and a knife for fishing line. Picnic Bay faces south, towards Townsville, so it is sheltered in northerly weather but exposed in southerlies and south-easterlies.

For divers staying on the island, it is a convenient alternative when Arcadia's bays are blown out by a northerly, and for macro enthusiasts it is one of the more interesting jetty dives in north Queensland.

Magnetic Island is reached by SeaLink passenger ferry from the Breakwater terminal in Townsville to Nelly Bay (about 20 minutes, frequent daily services) or by the vehicle ferry from Ross Street, South Townsville (about 40 minutes). Buses, hire cars and 'topless' mokes run from the Nelly Bay terminal to Arcadia, Horseshoe Bay and Picnic Bay. From Nelly Bay, drive or bus about 4 km south-west to Picnic Bay.

Park on the Esplanade near the jetty. Enter from the beach beside where the pylons start and follow the jetty out to the head at about 6 m. The jetty is Queensland Heritage listed and no longer a ferry terminal, but fishermen use it, so keep well clear of lines.

Boats must not anchor inside the no-anchoring area running from the jetty head to the southern tip of Hawkings Point.

Magnetic Island's bays are sheltered from different winds depending on which side they face. The dominant south-east trade winds (15–25 knots, April–September) chop up exposed eastern and southern bays and stir up silt, so the island's best diving comes in the calmer months of August–December and on mornings before the sea breeze. Visibility is usually 3–8 m and occasionally 10–15 m; it drops sharply after strong winds, big spring tides and wet-season rain (January–April) when Ross River and Burdekin run-off discolour the water.

Dive at slack water, ideally high tide. Sargassum seaweed blooms in the hotter months can smother shallow reef flats. Marine stinger season (box jellyfish and Irukandji) runs roughly November to May – wear a full-length stinger suit or wetsuit with hood and gloves, carry vinegar.

Stinger nets are installed at Alma Bay, Picnic Bay and Horseshoe Bay in season. Picnic Bay faces south towards Townsville and is affected by southerly and south-easterly winds; NQUEC notes the ideal breeze is from the north. Best recorded visibility is only about 5 m.

Enter at the beach end, zigzag slowly between the pylons out to the head at 6 m, checking the old metal straps and the fish-attracting device on the bottom, then return on the other side. At night, move slowly with a torch and a glow stick on the tank valve.

No regular operator; NQUEC club dives and independent divers. Pleasure Divers (Arcadia) hires gear. Nearest dive centres for gear hire, fills and local advice: Pleasure Divers Magnetic Island, Adrenalin Snorkel & Dive.