Merrial Beach is, in Parks Australia's words, Christmas Island's smallest beach and one of its prettiest: a pocket of white sand framed by rocky outcrops and grotto-like overhangs at The Dales on the west coast. The Dales – a series of steep valleys with streams and waterfalls such as Hugh's Dale – are a Ramsar-listed wetland, and the whole coastline here lies within Christmas Island National Park.

The beach is reached from the land by a rough track with some climbing, graded 3 by Parks, and only at low tide. Diving at Merrial is not part of the operators' published site lists, and there is no dedicated dive description; it is included here because it is a named coastal site that snorkellers visit and that boats can reach on calm west-coast days.

Underwater, expect the typical west-coast pattern: a narrow fringing reef of hard coral from the shallows, dropping to a steep slope and wall within a short distance of the shore. The west coast is regarded as having the clearest water around the island and less diving pressure than anywhere else, so the coral tends to be pristine. Reef fish – butterflyfish, angelfish, surgeonfish, parrotfish and wrasse – are abundant, turtles are common and the open water beyond the reef can bring reef sharks, dolphins and occasional pelagics.

Merrial suits experienced snorkellers and divers joining an exploratory west-coast trip in very calm conditions. Treat the information as indicative: confirm with an operator before planning a dive here. Photographers visiting at low tide come mainly for the scenery of the rocky overhangs and white sand.

Fly from Perth (about 4 hours, two to three flights a week, some via Cocos Islands) and hire a car – there is no public transport. Both dive centres are in The Settlement and launch their boats from the jetty/boat ramp at Flying Fish Cove, normally at about 8 am for a two-dive morning trip. From the cove the boat runs west along the north coast and then south down the west coast along the coast for roughly about 45 minutes to Merrial Beach.

There is no land access to the dive, and the vertical sea cliffs mean no exit other than the boat. Operators choose sites on the morning according to swell and wind. Walkers reach the beach from The Dales via a 4WD road and a rough Grade 3 track through dense vegetation with some climbing; the beach is accessible only at low tide – not practical with dive gear.

On the exposed west coast, a long run from Flying Fish Cove, so it is only dived on calm days. The site is sheltered from the south-east trades (roughly May–November) but wide open to north-westerly monsoon swell (December–April) and to long-period south-west groundswell generated in the Southern Ocean, which wraps around Egeria Point. Operators generally need less than about 1–1.5 m of swell and light winds to make the trip; the calmest spell is usually August–November.

The west coast has a reputation for stronger and less predictable currents than the north, and for the clearest water on the island (often 40 m+). Visibility can drop during red crab spawning (Oct–Jan). Cyclone season is November–April.

The beach itself is only reachable at low tide.

Descend on the reef off the beach, head seaward to the drop-off at 15–20 m, and return along the reef top. Snorkellers stay close in around the rocky outcrops at low tide in calm conditions.

No regular scheduled dives – visited occasionally by Extra Divers or CI Wet'n'Dry Adventures on calm west-coast trips; snorkelled by walkers at low tide.