5 Mile Reef is the deepest of the regularly named reef sites on the Terrigal list. The Terrigal Underwater Group describes it as a beautiful deep reef featuring sea whips in 33-38 m, and Muddy Puddle Diver calls it a popular deep dive with an interesting reefscape, plenty of fish life and fixed growth. Its distance offshore means clearer, bluer water than the inshore reefs on most days, which is a big part of the appeal.

The signature feature is the sea whips - long, unbranched gorgonian relatives that rise from the rock like whips and sway in any current, often with tiny gobies and shrimps living on them. Around them, sponges, gorgonian fans, ascidians and bryozoans build a dense deep-reef garden. The reef has more relief than the flat inshore grounds, with ledges, low walls and boulders that give shelter to bullseyes and cardinalfish.

Fish life includes schools of yellowtail, silver sweep and occasionally jack mackerel above the reef, red morwong and Maori wrasse on it, and kingfish, samsonfish and snapper cruising the edges. Wobbegongs are common, and the chance of grey nurse sharks in cooler months adds interest. At 33-38 m the dive requires careful planning: air no-deco limits are short, narcosis affects judgement, and the ascent is made in open water, often in current.

This makes 5 Mile suitable only for Deep-certified divers with recent experience, ideally on nitrox or following a planned decompression profile. For those divers it offers one of the best deep reef experiences on the Central Coast, well away from the crowds.

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.

As the name suggests, 5 Mile Reef lies well offshore from Terrigal - count on 15-20 minutes each way from The Haven in reasonable conditions. The skipper finds the reef with GPS and sounder and anchors or drops a shot.

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. Being further offshore, 5 Mile is the first site dropped when swell or wind builds.

Descend the line to 33-35 m, stay within sight of the line or run a reel if current is present, and explore the sea whip areas for no more than the planned bottom time. Ascend the line, completing any required stops and a 5 m safety stop.

Nitrox or planned decompression profile; redundant gas recommended; surface marker buoy essential for drifting ascents.

Occasional deep trips by Pro Dive Central Coast and Central Coast Divers for experienced divers; Terrigal Underwater Group dives it from members' boats.