Forresters Reef is one of the bigger reef systems on the Terrigal boat dive list. The Terrigal Underwater Group lists it at 29 m and describes an extensive reef system with plenty of marine life, while the Marine Life Network's Central Coast guide - which spells it Foresters Reef - lists it at 30 m and highlights clear waters and an attractive sponge garden. Its size means no single dive covers it, and different anchor points give quite different dives.

The reef sits deep enough that swell and kelp have much less influence than on the inshore reefs. Instead, the rock is covered in sponges of many shapes and colours - fans, fingers, cups and encrusting forms - with ascidians, bryozoans and small gorgonians between them. Low ledges and gutters cut through the reef and form the boundaries of the sponge patches, and the sand edges attract wobbegongs, fiddler rays and Port Jackson sharks.

Fish life scales with the reef. Schools of yellowtail and silver sweep hover over the top, bullseyes and one-spot pullers crowd the ledges, and red morwong, eastern blue groper and Maori wrasse cruise through. In warmer months kingfish and bonito may pass overhead, and in cooler months the chance of grey nurse sharks moving along the coast adds interest.

Nudibranchs are plentiful among the sponges. At 25-30 m the dive suits Advanced divers comfortable with open-water descents and depth management; nitrox is useful for extending bottom time. It is often chosen when conditions offshore are clear and calm and operators want to show a classic temperate sponge garden, and it rewards repeat visits because each drop point reveals a different part of the system.

All boat dives in this area launch from the Terrigal Haven boat ramp at the southern end of Terrigal Beach, tucked behind The Skillion headland. From the Central Coast Highway follow Terrigal Drive into Terrigal, then Kurrawyba Avenue and Terrigal Esplanade to The Haven, where there is a paid car park beside the ramp; Pro Dive Central Coast's shop is a short walk away and gear is loaded on the ramp or the adjacent beach. Private boats need a ramp with good parking early on weekends as the car park fills by mid-morning in summer.

From The Haven the boat runs north past Wamberal to the waters off Forresters Beach, around 10 minutes in reasonable conditions. The reef is large, so operators choose a drop point based on the day's current and the section they want to show.

Terrigal's offshore reefs are open to the Tasman Sea and are dived only when swell is below roughly 1.5 m; a north-east sea breeze building through the afternoon in summer and strong southerlies after a front are the usual reasons trips are cancelled, so morning departures are the norm. The Haven boat ramp is sheltered by The Skillion but the run out past the headland can be lumpy in a south-easterly. Visibility is best in late summer and autumn when the East Australian Current pushes warm blue water inshore, and worst after heavy rain when Terrigal Lagoon, Wamberal Lagoon and Avoca Lagoon open and stain the inshore water.

Winter water is cooler (around 15-17 °C) but often clear. Deeper offshore reefs also need manageable current - when the East Australian Current runs hard, skippers may skip them for sites closer in.

Descend the anchor line, note the reef features at the anchor, then swim into the current along the reef edge at 25-28 m. Turn at half gas or when no-deco time dictates, drift back a little shallower over the sponge gardens, and ascend the line with a safety stop.

Nitrox recommended to extend no-decompression time.

Pro Dive Central Coast (Terrigal Haven) runs boat dives from The Haven most days, weather permitting; Central Coast Divers also runs Terrigal charters; the Terrigal Underwater Group dives the site from club and members' boats. It is usually offered as a second dive or when conditions or demand favour reef sites over the ex-HMAS Adelaide.