Lost Lake East is a reef and wall dive on the stretch of north coast that locals call 'the dog's back', close to the Lost Lake cave system. It is one of the sites described in Diveplanit's series of Christmas Island dive reports, written after diving with Wet'n'Dry Adventures – whose founder, Hama, the author jokes, names sites on the spur of the moment before briefing them on the whiteboard.

The profile runs from a reef top at about 5 m, through a median depth of around 18 m, to 30 m on the wall. It is a consistent example of the island's north-coast drop-offs, with a band of healthy coral in the shallows and a steep face below. Bubble coral, plate and branching hard corals and sponges cover the reef, and the fish life is dense: peacock rockcod and honeycomb rockcod, black-spotted puffers (including the yellow colour form), schools of fusiliers along the wall, butterflyfish, angelfish and triggerfish. Crown-of-thorns starfish were recorded here – a reminder that even remote reefs have them in small numbers. Larger animals appear occasionally, including reef sharks, turtles and, in the wet season, whale sharks.

With no caves to worry about, Lost Lake East is a straightforward wall dive that suits intermediate divers. It is a useful alternative when the swell is too high for the cave entrances nearby but the coast is otherwise diveable, and it is a good place to look for pufferfish and rockcod for photography. As with most north-coast sites it is reliably calm during the south-east trade season.

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 past Smith Point and south-west along the north coast (the 'dog's back') along the coast for roughly about 18–20 minutes to the site.

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.

On the north coast, which is in the lee of the south-east trade winds from roughly April/May to November – that is the calm, reliable season here with glassy seas and 30 m+ visibility. From about December to March/April the north-west monsoon brings northerly and north-westerly swell (and occasional cyclone-generated swell) that can make the north coast undiveable and the Flying Fish Cove ramp unusable for days; Extra Divers treat February–April as peak swell season when trips are often cancelled. Any swell over about 1.5 m from the north-west quarter usually cancels the site.

Visibility dips after heavy rain run-off from the plateau and during red crab spawning (Oct–Jan) when plankton blooms. Tides are small (about 1 m) and rarely matter, but currents along the coast can pick up without warning.

Descend to the lip of the wall, drop to around 18–25 m and follow the wall, then ascend onto the reef slope and work back at 10 m before a safety stop on the 5 m reef top.

CI Wet'n'Dry Adventures – regular site (Diveplanit trip report); Extra Divers Christmas Island – dives the Lost Lake area.