Thompson Beach (Adelaide Plains crab flats)

Thompson Beach sits 56 km north of the Adelaide city centre and it is not a fishing platform in any normal sense — it is a crab-raking flat, and one of the two best known in South Australia. The gradient is the whole story: the beach shelves so gently that an adult carrying a rake can walk several hundred metres into Gulf St Vincent at low tide with the water still below the knee. The flats run one to three kilometres out, and reaching the far edge is a thirty-minute walk rather than a stroll. Under the water is a mosaic of clear sand, weed beds and seagrass meadows cut by tidal channels, and learning to read that mosaic is the entire skill. Blue swimmer crabs are the target, and in a gulf where calamari, garfish and snapper are all shut, they happen to be the one headline species still open on full limits. No source consulted names a finfish caught here, so this page does not invent one — it is a crab page, and on a still October Saturday the shack settlement empties onto the sand with buckets, tubs and small children to prove the point.

Raking is a walking sport and the tide sets the timetable. Go at the bottom of the low, walk out, and rake your way back in front of the flood — that is the method every South Australian source describes, and the lone travel blog recommending a high-tide arrival is outvoted three to one. Work water below knee depth, along the edges where clear sand meets weed, and hunt for dark patches: a crab digging itself in turns darker sand up from underneath, and that smudge is what you are looking for. The tidal channels are highways, carrying crabs into the shallows and back out again, so a channel edge is worth more than a hundred metres of featureless sand. Drag the rake across the patch, let the crab grab hold, then flip the rake over while it is still hanging on — blue swimmers oblige almost every time. Measure each one as it comes up, check the flap for eggs, and put berried females straight back. Serious locals fit floats and wheels to their tubs and tow them on a rope from the waist, which frees both hands for the rake and looks ridiculous for about four minutes, until the first time you try to carry a full tub half a kilometre.

Blue swimmer crabs are the catch, and the rules are the same in every South Australian zone. The minimum is 11 cm across the carapace measured at the base of the largest spines, the personal daily bag is 20, the boat limit is 60 when three or more people are fishing, and berried females are protected at all times. There is no recreational seasonal closure on crabs, which is exactly what makes this coast worth the drive at the moment. Crabs must be measured as soon as they are caught, so the gauge goes out onto the flat with you. Sand crabs — light brown with two dark spots on the back — appear in numbers around Adelaide; they carry a 10 cm minimum and a bag of 10 in the Gulf St Vincent zone. The wider gulf picture is stark: southern calamari and southern garfish are both closed to recreational fishers in Gulf St Vincent until further notice, and snapper is closed until at least 30 June 2027. Fisheries officers work these flats regularly for undersize crabs and over-bags, a sentence written entirely for the people who leave the gauge at home.

Check the tide range before leaving Adelaide, not after arriving. Gulf St Vincent runs dodge tides around the neaps, and one of those turns an hour's drive into a walk on a beach that never drains. A big low is the whole product here, and the tide panel earns its keep before you put the rake in the boot. Wind is the second gate, and a chop over the flat is reason enough to postpone. Sunglasses are functional gear here, because glare off six inches of water is what stands between you and seeing anything at all. A warm, still, overcast day on a big low is the combination worth driving for, and late summer into early autumn is when the water is warmest and the crabs are busiest. Carry more drinking water than seems reasonable — there is no shade out there, and the walk back is always longer than the walk out.

Thompson Beach is reached through Dublin off Port Wakefield Road and then the Thompson Beach road, about 56 km north of the Adelaide city centre. There is a foreshore car park and two public toilet blocks, one toward each end of the settlement, and that is the complete facilities list. There is no jetty, no boat ramp, no kiosk and no documented lighting — this is a walk-on flat in a low-density shack locality subdivided in 1980, and it has stayed that way. It is genuinely kid-friendly in one specific sense, in that the water stays below knee height for the better part of a kilometre, and thoroughly unfriendly in another, because the walk is long, hot and unshaded with nothing at the far end but more flat. Wheelchair access to the activity itself is not realistic, since the whole thing is wading soft sand and weed. The flats lie within the Adelaide International Bird Sanctuary, a feeding, resting and nesting ground for local and migratory shorebirds including critically endangered species, so keep to the sand and respect the posted restrictions. The water off the beach is marine park habitat protection zone, where fishing and crabbing are both allowed, with a no-take sanctuary zone a few kilometres down the coast toward the Light River and Port Gawler. The nearest no-entry zone is about 7 km up the coast toward Port Parham, and no part of this flat is inside it. Check the current zoning on the Department for Environment and Water marine parks map before walking a long way out.

The order of importance is tide, then wind, then clarity, and nothing else comes close. The bigger the low, the more flat there is to walk, and the standard program is to be on the sand at the bottom of the tide and working the flood back toward the car park. A dodge tide is a day to stay home, because a flat that does not drain is a flat you cannot rake. Wind is the reason most planned trips get called off, because nothing on the bottom shows through a chopped surface. Water clarity and warmth drive the activity — a hot, sunny, still day has the crabs moving, and the peak of the raking is late summer and early autumn on the warmest water. An overcast, windless day is the sleeper option, since the glare drops away and the crabs are still there. Winter thins the blue swimmers out and the sand crabs fill the gap from about May to September.

The tide is the hazard, and it is a real one. Walking a kilometre out onto a flat that floods in behind you is fine right up until it is not, so the discipline is to work the flood back toward the shore instead of raking into it. Shoes are not optional, because razor-sharp shellfish, rocks, spined fish, stingrays and blue-ringed octopus all live on this bottom, and everyone shuffles rather than strides. Stay off the seagrass meadows, where the mud will swallow a shoe. Sun and dehydration are the quiet ones, with no shade anywhere, no water out there and a long return walk on tired legs. A windy day is a safety problem too, because you cannot see what you are about to step on. Handle crabs from behind the carapace or with tongs, because the claws are not decorative.

Blue swimmer crabs run from about October to April, peaking in late summer and early autumn when the water is warmest. Within a day, go at the bottom of a big low tide and rake your way back in front of the flood. Skip the dodge tides around the neaps, when the gulf barely moves and the sand never uncovers.

Blue swimmer crabs must be at least 11 cm across the carapace at the base of the largest spines, the personal daily bag is 20, and the boat limit is 60 when three or more people are fishing. Berried females go straight back in the water. Crabs must be measured as soon as they are caught, and fisheries officers check these flats regularly.

No source consulted names a finfish caught here, so this page treats it as a crab-raking flat rather than a fishing spot. It is also worth knowing what is shut in this zone — southern calamari and southern garfish are closed to recreational fishers in Gulf St Vincent until further notice, and snapper is closed until at least 30 June 2027.

A crab rake, a crab gauge, a tub of seawater, shoes you do not mind ruining and polarised sunglasses. Hoop nets are allowed as well, up to ten of them if no rod is in use or three if there is, and drop nets are capped at three per person. Bait in any net must be fish or fish-based, because meat and chicken are illegal in South Australian crab nets.

The water stays below knee height for the better part of a kilometre, which makes it one of the gentler outings on the gulf, but nobody should be out there barefoot. Razorfish, rocks, spined fish, stingrays and blue-ringed octopus are all on the bottom, so everyone wears shoes and shuffles. Watch the flood tide, carry water, and turn around earlier than feels necessary.