The Basin is the best-known picnic and camping spot on Pittwater's national-park shore, a sheltered beach with a tidal lagoon behind it on the eastern side of West Head, reached only by ferry from Palm Beach, by boat, or on foot down the 2.8 km Basin Track. NPWS describes a sheltered beach and inland lagoon ideal for children's paddling and swimming, a campground with amenities, barbecues and the Bairne walking track, and day-visitor landing fees of a few dollars. What is under the water follows from the setting: the netted lagoon is a shallow sandy pool of no interest to divers, but the beach fronting Pittwater slopes into Posidonia and Zostera seagrass at 2–4 m, with rocky sandstone points on either side of the bay dropping to 5–6 m before the estuary floor slides away into the deep channel.

The seagrass is nursery habitat for bream, whiting, luderick, leatherjackets, juvenile snapper and, at the right season, seahorses and pipefish; the rocks hold octopus, cuttlefish, blue-ringed octopus and small wrasses; stingarees and flathead lie on the sand; and the campground's wallabies watch from the grass. Water quality after rain is the constraint, and the Hawkesbury's turbidity means 2–6 m is the usual range. It suits families camping at the Basin, snorkellers, and Open Water divers on a Pittwater boat looking for a calm, shallow paddle with a barbecue afterwards; anyone expecting Sydney's reef diving will be disappointed.

Depths and layout are inferred from the NPWS pages and estuarine geography; confidence is low.

The Basin has no road access. Take the regular Palm Beach ferry (from Palm Beach wharf on the Pittwater side, about 20 minutes, gear allowed at the operator's discretion), a water taxi, or a private boat, or walk the 2.8 km Basin Track down from the West Head Road car park in Ku-ring-gai Chase National Park (park entry $12 per vehicle; day landing fee $3 adult, cash). The campground has amenities and the lagoon is netted for swimming.

Enter from the beach into Pittwater proper for the seagrass and rocky points; the lagoon itself is a shallow paddling pool. Exit onto the beach. Gates to West Head close at night.

Entirely sheltered from ocean swell on the western shore of Pittwater; only a strong easterly or north-easterly wind chops the beach. Visibility depends on the Hawkesbury: 5–6 m on a clean winter flood tide, 1–2 m after rain when the whole estuary runs brown and NPWS advises checking the Beachwatch water-quality forecast before swimming. Tidal flow is gentle in the bay; the flood brings the cleanest water.

Boat and ferry traffic at the Basin wharf on weekends.

Enter from the beach and follow the seagrass and sand at 2–4 m toward the rocky point on either side of the bay, searching the weed for seahorses and pipefish and the rocks for octopus and cuttlefish, to a maximum of about 6 m off the points; return along the shore inside the moorings and surface at the beach.

No operator; campers, snorkellers and private boats. Fills at Dive Spear and Sport, Mona Vale.