Lilli Pilli is a gentle estuary dive about 4.2 km inside Port Hacking and one of the best places in Sydney to see White's seahorses. It lies at the end of Lilli Pilli Road, where a quiet waterfront reserve, the Sea Scouts' boat ramp and a swimming enclosure net front the river. From the ramp the bottom deepens steadily westward: two to three metres about five metres out, then 5–6 m, 9–10 m and shortly 12–13 m.

The seabed is sand with patches of seagrass and small rock outcrops, becoming silt with isolated rocks deeper down, and there are large rock ledges further out. The swimming enclosure net and its pylons are the key feature for navigation and for marine life. White's seahorses cling to the net and the seagrass – McFadyen once counted 63 on one dive in April 2005 – and they are the main reason most people come.

Other residents include yellowtail kingfish, moray eels, cuttlefish, eastern rock blackfish, blue gropers and several species of rays, along with many small invertebrates for macro photographers. Relics of the waterfront's long history turn up too: old ceramic jars and sherry bottles, and, since February 2024, a scuba-diver statue on the bottom. The water of Port Hacking is generally clear, with visibility sometimes over 15 m, and the current is minimal, unlike at nearby Shiprock.

The downsides are the slippery ramp and hundreds of pieces of fishing line near the wharf. There are no facilities at the site, though Caringbah has cafés. White's seahorse is a threatened species in NSW, so divers must not touch or move them and should avoid shining lights directly on them.

It suits beginners, night divers and photographers.

From Caringbah drive down Port Hacking Road South until it branches into Lilli Pilli Road and follow it to the end. A gated tarred roadway (open 6 am–10 pm) runs parallel to the waterfront with parking alongside. Gear up at the car and enter via the sandstone steps and the boat ramp belonging to the local Sea Scouts, who have historically allowed divers to use it – be courteous and keep it clear.

The ramp can be very slippery.

Deep inside Port Hacking, the site is completely sheltered from ocean swell and can be dived in any wind – a good option when the coast is blown out. Port Hacking tides run about 20–40 minutes later than Fort Denison predictions; heavy rain and big easterly seas delay the turn further. Unlike Shiprock, the current here is minimal, but high tide still gives the clearest water.

Port Hacking is generally clear, sometimes over 15 m, but heavy rain brings runoff and silt that can take days to settle. Weekend boat and jet-ski traffic is the main nuisance.

From the ramp head west at depth over sand and rock outcrops (5–6 m, then 9–13 m), checking ledges. Near the pylon holding the swimming-enclosure net, explore north-west over sand and silt, then follow the net south looking for seahorses on it. Shallow up to about 5 m near the wharves and return along the eastern side of the net to the ramp.

Pro Dive Cronulla and Abyss run seahorse and night dives here; many clubs and photographers dive it independently.