Cateran Bay on Border Island, east of Whitsunday Island, is one of the prettiest snorkelling bays in the outer Whitsundays, and 100 Magic Miles lists it among its top ten snorkel spots. The guide describes good hard coral cover in shallow water to 6 m, small walls and bommies, and 'large beautiful plate coral', with depths of 2–12 m and visibility of 2–12 m. Fish are average in number, but larger sweetlips and cod shelter under ledges, and the shallow coral is easily enjoyed by snorkellers of any ability.

The bay's shelter means current is minimal inside, making it a calm, easy site for families and new divers. The entrance is another matter. Strong currents run at the bay's mouth and around its north-western tip, and divers and snorkellers should stay inside.

Border Island's position on the eastern edge of the Whitsunday group exposes it more to swell and wind than the inner bays, so it is visited mainly on calm days, often by sailing trips combining Whitehaven Beach and Hill Inlet with a snorkel stop. Cateran Bay lies further from Airlie Beach than the Hook and Hayman sites and is less frequented by dive boats. Its coral was not singled out in reports of Cyclone Debbie damage, but condition should be checked.

For snorkellers and relaxed divers on a sailing trip, it offers some of the best shallow plate coral in the islands. Snorkellers should enter from the boat near the middle of the bay and work towards the shallows, keeping the entrance behind them, and stinger suits are essential in the warmer months as elsewhere in the Whitsundays.

Boat only. Border Island lies east of Whitsunday Island, about 30 nautical miles from Airlie Beach – roughly about 1–1.5 hours 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. Cateran Bay is a common stop for sailing charters combining Whitehaven Beach and the outer islands.

Whitsunday island reefs are exposed to different winds depending on aspect: the dominant south-east trades blow 15–25 knots April–September, and northerlies are common October–March. Tidal currents through the islands are strong on spring tides (range up to about 4 m), particularly at bay entrances, points and passages – plan dives at slack water and neap tides. Visibility is usually 5–15 m, dropping after strong winds, big tides and wet-season rain.

Manta rays visit May–September. 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).

Border Island is on the eastern edge of the group and more exposed to swell. Minimal current inside Cateran Bay but strong currents at its entrance and north-western tip.

Stay inside the bay: snorkel or dive over the shallow hard coral to 6 m, then visit the small walls and bommies along the sides to 10–12 m. Avoid the entrance and north-western tip where current runs.

Sailing charters and bareboats (regular in calm weather); occasional dive boats. Nearest dive centres for gear hire, fills and local advice: Whitsunday Dive Adventures, Explore Group, Ocean Rafting, Red Cat Adventures, Cruise Whitsundays.