Mackerel Bay is one of the Hook Island bays that come into their own when the usual south-easterly pattern breaks down and northerlies blow, typically in the warmer months. 100 Magic Miles lists it with depths of 2–12 m and visibility of 2–10 m, describing good coral cover in shallow water that drops off to scattered bommies forming canyons. Fish are medium-sized and present in quite good numbers. The layout gives a straightforward dive: a shallow coral terrace for snorkellers, then a drop to bommies and the canyons between them, where fish shelter and divers can weave between coral heads.

Expect coral trout, sweetlips, parrotfish, fusiliers, damsels and wrasse, with turtles and the occasional reef shark. The canyons add enough structure to keep a dive interesting despite the modest depth. Conditions are the key.

The bay is exposed to southerly winds and is therefore used mainly in northerlies, and visibility depends heavily on the tide; the guide recommends neap tides for the best snorkelling. Tidal flow around Hook Island is significant on spring tides. Mackerel Bay sees fewer day boats than the northern Hook sites because it is used only in certain wind conditions, so it tends to be dived by bareboats, overnight sailing trips and dive boats looking for a sheltered option on a northerly day.

Like other Hook Island fringing reefs, it may have been affected by Cyclone Debbie in 2017, and coral condition should be checked. It is a pleasant, easy dive for Open Water divers and a good snorkel on the right day.

Boat only. Northern Hook Island is about 22–28 nautical miles from Airlie Beach – roughly 45–75 minutes by fast day boat from Coral Sea Marina or Port of Airlie, or about 1 hour from Hamilton Island marina. Day tours that stop here include Ocean Rafting, Red Cat Adventures (Thundercat), Whitsunday Dive Adventures and Explore Group (from Airlie and Hamilton Island); overnight sailing and bareboat charters also visit.

Private and bareboat skippers must use the public moorings (time-limited, first come first served) and observe no-anchoring areas marked by reef protection markers; bareboat operators restrict where hirers may go. Parking at Airlie is available near Coral Sea Marina and the Port of Airlie. Mackerel Bay is mainly used in northerly winds.

The eastern and southern Hook Island bays are the mirror image of the northern bays: they are used when northerly winds blow (common October–March) and are exposed to the south-east trades that dominate April–September. Tidal currents through the islands are strong on springs (range up to about 4 m) and visibility is closely tied to the tide – best on neap tides, poor on big springs and after strong winds or wet-season rain. Typical visibility 2–12 m.

Marine stinger season (box jellyfish and Irukandji) runs roughly November to May – wear a full-length stinger suit or wetsuit with hood and gloves, carry vinegar. Cyclone season November–April; tropical lows and cyclones can close sites and damage coral (TC Yasi 2011, TC Debbie 2017). 100 Magic Miles: popular during northerlies, exposed to southerly winds; snorkelling best on neap tides.

Start over the shallow coral, follow the drop-off down to the scattered bommies and canyons at 8–12 m, and return shallow along the reef edge.

Bareboat and overnight sailing charters (main users); day dive operators (Whitsunday Dive Adventures, Explore Group) visit occasionally when wind direction suits.