Balmoral Baths is the classic Sydney seahorse dive, an ocean-pool-style netted enclosure off the southern end of Balmoral Beach in Hunters Bay that has been counted, photographed and studied more than any patch of net in the country. The enclosure is timber pylons with a large-mesh net inside and, in parts, a finer mesh outside, curving rather than square, with gaps of one to two metres between pylons; the bottom is sand and seagrass from about 1 m at the beach to just over 4 m at the outer net, 5 m at high tide. It is inside Middle Harbour, sheltered from almost everything, and the parking, shower and cafes are within 100 m.

The reason to dive it is White's seahorse, Hippocampus whitei, the endangered Sydney endemic that lives on the net mesh and pylons: 87 were counted on a single night dive here, and although numbers fluctuate with net maintenance and storms the baths remain one of the species' strongholds, along with Clifton Gardens and Manly Cove. Around them are pygmy and fan-bellied leatherjackets, sole and flounder on the sand, yellowtail, sea pike and bream inside the net, octopus and cuttlefish at night, and blue-ringed octopus often enough that gloves and care are advisable. Pipefish, decorator crabs and nudibranchs live on the pylons.

It is a night dive above all; by day the same circuit works but the seahorses are harder to pick out and swimmers crowd the enclosure. The net has large holes and offers no real protection from anything, which is irrelevant to divers and worth knowing for swimmers. Depth never exceeds 5 m, so bottom time is limited only by cold.

Balmoral suits complete beginners, course groups, snorkellers and macro photographers, and it is the standard first night dive for several north-shore dive schools.

From Military Road at Mosman shops take Raglan Street downhill to The Esplanade at Balmoral. Right-angle parking along The Esplanade about 200 m south of the Raglan Street corner is the closest to the baths (metered by day, busy in summer; free and quiet at night), with more parking opposite and further along. Walk 50 m down to the sand and into the water beside the enclosure.

A freshwater tap and shower are on the wharf steps beside the baths. Exit back onto the beach.

Deep inside the harbour these sites see no ocean swell; only a strong southerly or south-easterly wind raises a chop, and even then the dive usually goes ahead. What matters is water quality and tide. Dive on the incoming tide or at high water, when the flood brings cleaner ocean water up the harbour and the shallow margins have enough depth; low tide exposes rock and shortens the dive.

Visibility is normally 3–7 m and can reach 10 m on a winter flood; after heavy rain the harbour runs brown for several days and visibility drops to a metre. Boat traffic is heavy on summer weekends. Night dives are the best dives.

Balmoral faces east down Middle Harbour toward the Heads and is one of the calmest beaches in Sydney; only a strong easterly wind or a very big easterly swell creates any surge on the net. High tide adds a metre of depth to a very shallow site and is strongly preferred.

Enter at the south-eastern corner of the baths and work around the outside of the curved net anti-clockwise at 2–4 m, checking the mesh and every pylon for seahorses and the sand between for sole, octopus and blue-rings; a full circuit takes about 40 minutes. Finish inside the enclosure over the seagrass. Above-water lights make the timber structure visible at night; stay inside or beside the net to keep clear of boats.

Dive 2000 (Neutral Bay), Frog Dive, Plunge Diving and Pro Dive Manly use Balmoral for confined-water course dives, Discover Scuba and guided night dives; Dive Centre Manly occasionally. Very popular with independent night divers and photographers.