Prison Gardens is on the eastern side of the southern atoll, near the small island known as Prison Island – a sandy cay whose name dates to the Clunies-Ross era and which lagoon tours visit for its history and nursery reefs. The official Cocos tourism listing gives the dive range as 14–35 m and describes it as a 'wind-protected haven' dived especially in the summer months. The reef is characterised by plate and other hard corals in good condition, forming broad tables that overlap across the reef.

The main fish attraction is large schools of big-eye trevally, which are curious and tend to circle divers; the courtship displays seen on Cocos – paired fish darkening and swimming close together – are sometimes observed. Scientific coral-monitoring buoys installed at the site are a reminder that the reefs of Cocos are studied as a reference for healthy reef systems. The official snorkelling guide also notes Prison Island as a juvenile fish nursery.

Because it is further from West Island than the western and northern-rim sites and faces the trade winds on the approach, Prison Gardens is less frequently dived and is mostly a summer site, adding variety for divers staying a week or more. Depth can be tailored: newer divers keep to 14–20 m on the coral, while experienced divers can explore deeper to 35 m. Visibility is typically 20–30 m.

The site suits Open Water divers in calm conditions. Divers who want to see Prison Island itself can join a lagoon tour (Cocos Blue Charters or Cocosday Tours) on a non-diving day and snorkel the shallow nursery reefs around the cay, which makes a good complement to the deeper dive.

Fly to West Island on the twice-weekly Virgin Australia service from Perth (usually routed via Christmas Island; allow 7–10 days on the islands to absorb weather and flight delays). Cocos Dive collects divers from West Island accommodation in the morning (pickup around 8 am, departure about 9 am) and runs its boats from West Island into the lagoon. Prison Gardens is on the eastern side of the atoll near Prison Island, south of Direction Island, which means the longest lagoon crossing from West Island.

Cocos Dive visits in the summer months when the trades ease. Moorings or live-boat drop; no shore access. Prison Island itself is a small sandy cay that lagoon tours visit.

Cocos has two seasons. The south-east trades blow steadily from roughly April/May to October, often 15–25 knots, which chops up the lagoon and pushes swell onto the eastern and southern outer reefs; divers are then kept to sheltered sites. The doldrum season (November to March/April) brings lighter, variable winds, flatter seas and the widest choice of outer-reef sites, and is the best time to dive, though it is also the tropical cyclone season and squalls pass through.

The eastern side of the atoll faces straight into the south-east trades, so its outer reefs and passages are rough and often undiveable from April to October; they come into their own on calm doldrum-season days. The official listing describes the reef itself as a wind-protected haven once reached, but the site is preferred in summer.

Descend onto the reef at about 14 m and work along the plate corals to 20 m, watching for big-eye trevally schools. Look for the coral-monitoring buoys. Deeper water to 35 m is available for experienced divers, but the best coral is shallower.

Return along the reef for a safety stop on the reef top.

Cocos Dive (Dieter Gerhard, West Island, operating since 1990) is the only scuba operator on the islands and the only way to dive this site. It runs seasonal two-dive day trips with lunch and a surface interval on Direction Island, maximum 10 divers per trip; sites are chosen on the day according to wind, tide and diver experience. Trips book out well ahead and courses are currently suspended, so arrive certified.