The Western Boat Passage is the channel through the north-western rim of the atoll, between West Island and Horsburgh Island, used by boats moving between the lagoon and the ocean. Tourism Western Australia's Cocos feature lists it as a stop on Cocos Blue Charters' glass-bottom boat tours, and the tidal exchange that runs through it feeds the reefs on either side – the Cabbage Patch, Rose Wall and Ski Run dive sites all sit near it, and their currents and visibility depend on the passage's tide. Clear ocean water pushes in on the incoming tide, bringing visibility and fish, while the outgoing tide carries lagoon water out.

From the glass-bottom boat, visitors see the coral and fish along the edges of the passage; where the skipper judges it safe, snorkelling may be offered, typically near slack water or as a supervised drift. It is not a place for independent swimming: tidal streams and boat traffic make it unsuitable without a skipper. For certified divers, the nearby Cocos Dive sites are the way to experience this part of the atoll underwater.

Understanding the passage helps plan those dives: Cocos Dive generally times the north-western sites for the incoming tide, when the passage carries clear oceanic water onto the reefs, and avoids the strongest flow around mid-tide. On glass-bottom tours, the passage is also a good place to watch for turtles surfacing and for dolphins, which travel through it between the lagoon and the open sea.

Reached only by boat from West Island, a short run north through the western lagoon. Tourism WA lists the Western Boat Passage as a stop on Cocos Blue Charters' glass-bottom boat tours. Cocos Dive's north-western dive sites – Cabbage Patch, Rose Wall and Ski Run – lie close by.

The skipper times any snorkel with the tide. Book ahead – tours are seasonal and small.

Lagoon snorkelling is possible year-round, but the south-east trades (April/May–October, often 15–25 knots) chop the lagoon, stir up sand and make swimming harder; the doldrum season (November–April) usually brings glassy conditions and the clearest water. Tides matter more than swell inside the lagoon: shallow flats can become too shallow at low water, and tidal streams run through channels between islands. Heavy tropical showers are brief and have little effect on visibility because there is no river run-off.

The passage carries tidal flow in and out of the lagoon; snorkelling is only sensible near slack water or as a boat-supervised drift.

View from the glass-bottom boat; snorkel only if the skipper judges the current safe, ideally as a supervised drift near slack water, with the boat following.

Cocos Blue Charters – glass-bottom boat and snorkel tours; Cocos Dive's dive sites nearby.