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Bare Island

Bare Island, La Perouse: 211,000 square metres mapped in detail, with the tidal currents, a 3D version and how to read it.

A huge site: 211,000 m² of it, of which the island itself is only a tenth. Twenty dives, four months and around 200 hours produced this map — against tidal currents, boat traffic, and at least one boater who pulled me to the surface by grabbing my GPS.

Conditions today: this site is BI West and BI East on the VIZ Forecast.

The Bare Island map

Download the PDF recommended, 85 MB Whole site (bitmap) Detail: west Detail: south Detail: east Detail: north The wider area JPG

The PDF is worth the download despite its size — it zooms without limit, which the bitmap cannot. All bitmaps are 1:1000, so in a photo editor one millimetre is one metre. GPS positions are WGS84 throughout.

The site in detail

A 3D version

Open Bare Island in 3D → The map draped over the NSW Government's 2018 LiDAR survey of the seabed. Turn it, zoom in, and point anywhere to read the depth. Bare Island in three dimensions

Tidal currents on the south-west side

If you do not know the SW side of the island, be aware of strong currents around the change of tide, as the whole of Botany Bay empties and fills to the west. Eastward going towards low tide, westward going towards high.

The current can be strong enough to stop you making progress. Combined with 17–18 m of depth, that means running out of air a long way from the exit with boats overhead. Avoid the area marked red unless it is slack water, or unless you are drifting deliberately from one side of the island to the other. The timing is not always what you expect, so assess it on the day and divert if you need to.

Thanks to Michael McFadyen for his help with this, and see his explanation of the tide here.

The tidal current zones

How to read the map

It is a living document. The site was surveyed between October 2020 and February 2021, but sandlines and exposed low reef move with current and swell, so the map is updated when time allows — check here for the latest rather than keeping a copy on your phone.

The point of it is safety: planning the start of the dive, the route, and above all the end of it. How many times have we surfaced a long way from where we meant to be? With a plan, adventurous divers can also go further.

Fish are deliberately not marked. Partly to leave something to discover, and partly to avoid over-diving the weedy seadragons, red indianfish, sea turtles and eastern blue devils that are top of most people's lists. Mapping a site changes where divers go; this keeps that from turning into a procession. The size of the place and the currents will do the rest. Forty-one tyres are mapped, though.

Reference photographs

Each is keyed to a grid position on the map.

1 · The crossroad — left for the shortcut, right to continue west to the first cave. X60 Y45 2 · Cave, South Bommie. X100 Y128 3 · Anchor, lower centre, north of the South Bommie. X73 Y110 4 · Classic eastern-side scenery at about 5 m: kelp and sandstone holed by sea urchins. X93 Y84 5 · Finger sponges, common on the east side — here at the saddle between the island and the Bommie. X90 Y105 6 · Plough anchor on the Bommie. X102 Y157 7 · The big C on Isolated Reef 1. X25 Y52 8 · The crumble, on the saddle between the island and South Bommie — a useful reference for crossing 9 · An abandoned cray trap, SE of the South Bommie. X120 Y180 10 · The concrete block and chain at the back of the Corner Cave. X43 Y52

A great sea pen, Sarcoptilus grandis, on the sand east of the South Bommie — about 60 cm tall, feeding by filtering water, which the video makes obvious.

Going further

If the site is new to you, dive it with someone who knows it, and read Michael McFadyen's pages on Bare Island for a great deal more on the individual dives.

For the marine life, spend an hour in John Turnbull's gallery of 1,700 photographs — he is a marine ecologist and researcher at UNSW, and the collection is public on his Flickr. He also wrote a presentation on the Bare Island ecosystem and why it matters to the proposed cruise terminal at Yarra Bay.

Naming, and thanks

Most names already in use are kept. A few are new — The Boomerang, because only with a map can you see the shape from above. Giulia's Pencils are named after my daughter, a designer living in Italy: every time I am lost in the indistinct shallows with the gauge in the red, those parallel cracks point the way home.

Thanks to Greg Ryan and Michael McFadyen, whose knowledge of this site is extensive, and to every diver in the car park whose interest kept me going. This map is for you too.

Questions or corrections: Marco Bordieri on Messenger.