Big Peninsula, known locally as Big P, is the horseshoe-shaped bay on Great Keppel's north-east point and the island's everyday dive site. It is sheltered from the prevailing south-easterlies, shallow (mostly 12-14 m) and close to the dive base, which makes it the operator's choice for training, refreshers, night dives and days when nothing else is diveable. The bay's reef runs around its edge onto a sandy bottom.

Coral gardens line the shallows, with sea whips and sea cucumbers on the sand and rubble. The sand is the place to look for bull rays and blue-spotted rays, and moray eels peer out of the reef edge. At night the site comes alive with crustaceans, hunting morays and sleeping fish.

On a running tide the edge of the bay can be dived as a gentle drift, which adds a little variety. Visibility is typical of the inner islands and varies with wind and tide. Big P is not a site to travel for on its own, but it is a comfortable, dependable reef that makes a good first dive in the Keppels, a very good night dive and a place for new divers to build confidence before tackling the outer rocks.

Great Keppel Island (Wop-pa to the Woppaburra traditional owners) has been through several phases of resort development and closure, and today the dive operation is small and relaxed, which suits a low-key site like this. Big P is also where many divers first meet the Keppels' olive sea snakes, which are curious rather than aggressive and usually swim away after a close look. Divers staying several days often return here for a night dive once they have seen it by day.

Drive 40 km (about 40 minutes) from Rockhampton to Yeppoon, then 7 km south along the Scenic Highway to Keppel Bay Marina at Rosslyn Bay Harbour, where there is free and paid parking. Freedom Fast Cats and Keppel Konnections ferries run to Great Keppel Island (Fisherman's Beach) in about 30 minutes; Keppel Dive & Water Sports picks up certified divers from the island. Big Peninsula ("Big P") is about 10-15 minutes by dive boat around the island from Fisherman's Beach, or roughly 35 minutes by private boat from Rosslyn Bay.

Boats anchor in the bay. Divers staying on Great Keppel can also reach the headland by walking track, but boat access is normal.

Keppel Bay is exposed to the prevailing south-east trades (strongest April-September) and to summer northerlies. The bay is protected from south-easterlies and is one of the sites used when the outer islands are blown out. Strong northerlies (common in spring and summer afternoons) make it choppy.

Tidal currents across the mouth of the bay allow a gentle drift on the right tide. Visibility is often 5-12 m and is reduced after strong winds or rain.

Descend from the anchor to the sand at 10-12 m and follow the reef edge around the bay, looking under ledges and in the sand for rays. Return along the shallower coral gardens and finish the safety stop in 5 m.

Keppel Dive & Water Sports (PADI 5 Star, based on the Spit at Great Keppel Island next to Great Keppel Island Hideaway) runs guided boat dives to the Keppel sites most days, weather permitting, plus courses and Discover Scuba; site choice is made on the day according to wind. Private boats from Rosslyn Bay also dive here. Big Peninsula is a regular site for courses, night dives and shore-style boat dives.