Quarantine Station Reef lies off the Point Nepean Quarantine Station, which took in immigrant ships from the 1850s until about 1950 and whose long jetties, hospital wards and cemetery still stand on the shore of Ticonderoga Bay. For a century ships anchored off the station to land passengers, and the seabed here is a record of that: the Scuba Doctor listing counts six large anchors on the site and 'scattered artefacts including bottles, china plates, bowls, cups, clay jugs and black powder gun shells', with intact plates from the White Star Line, P&O and other companies among the finds. All of it is protected and must be left in place.

The reef itself is a ridge with its top at about 12 m running east–west parallel to the current, and a southern drop-off to 20–22 m, carrying soft corals and sponges on the ledges; the listing is honest that much of the surrounding bottom is sand with 'limited reef area', and that the ridge is the attraction. On the sand are spider crabs – in vast aggregations in late autumn and winter – and stingrays, and dolphins and seals pass through the bay regularly.

The site is normally run as a drift rather than a slack-water dive – 'the best time is when the water is moving' – with the group on a float line and the boat following along the ridge; it is one of the standard drift-diving instruction sites for the Portsea operators, being five minutes from the pier and sheltered from most weather. Cattle Jetty Drift and Artefacts Flood, both nearby, cover the same historic seabed toward the old cattle jetty and further into the bay.

Boat access, though the listing notes shore access is possible (the Quarantine Station foreshore in Point Nepean National Park is open to the public by day, but it is a long walk and the reef is 200–300 m out – in practice everyone dives it by boat). Charters from Portsea Pier are on site in five minutes; private boats from Sorrento ramp in 15. The site is run as a group drift under a flagged float with the boat following, parallel to the shore; the South Channel and the ferry route are just to the north, so the float and flag are essential.

Unusually for the Heads, this is not a slack-water site: the listing says it is diveable 'on any tide' and that 'the best time is when the water is moving' – a drift on the flood or ebb at 0.5–1 knot, with slack water also usable as a stationary reef dive. Slack water at Port Phillip Heads does not coincide with high or low water: it falls roughly three hours after high or low water at Point Lonsdale, and the usable window is typically 20–40 minutes. Use the Ports Victoria / Port of Melbourne slack-water predictions for The Heads (also republished by charter operators and WillyWeather 'Rip Bank') rather than a standard tide table.

Ticonderoga Bay is sheltered from southerlies and westerlies by the Nepean peninsula and is workable in most weather; a strong northerly chops it up and drops visibility to a few metres. Year-round; best in autumn.

Group descends the float line onto the reef top at 12 m up-tide of the site and drifts east–west along the ridge, dropping over the southern side to 18–20 m to look under the ledges and out onto the sand for anchors and artefacts, then back onto the reef top; the boat follows the float and retrieves the group after 40–45 minutes.

Dive Victoria Group and Bayplay (Portsea) – frequent drift and second dive, 5 minutes from the pier; Red Boats – occasional; private boats from Sorrento. A common site for drift-diving instruction.