Adult catching the late afternoon sun. The warren is roughly halfway between this geological site of national significance and the rudimentary AWD vehicle car park at the end of the access road.
FTR we saw many, many wombats in and around Hiltaba during our few days spent there (and the great majority were alive despite my recent postings of several road killed ones, which we saw outside the boundary of the actual Hiltaba Nature Reserve, while driving to our accommodation late afternoon).

Port MacDonnell. Shallow limestone reefs and substrate which lowers wave energy. Small rocky bay surrounded by reef. In rock pool and among rocks at medium tide on inter-tidal limestone reef. Rocky headlands with small sand pockets.

Interesting encounter in interactive terms. The subject seems unfazed by the proximity of the Southern Keeled Octopus (doesn't prove that this Octopus species never eats Crested Pipefish, but maybe they usually don't, and pipes generally wouldn't rate highly in protein calorie density cw many other readily available prey in the habitat they often coexist in).And in the background is an Ikeda genus worm, which FWIW seemed reluctant to retract even when I got much closer (there were a few such worms feeding during this dive and I suppose they were doing so at a time of low predation risk;tide almost fully out and relatively little fish activity, also middle of day with improving water clarity inside the platform reef).

This goatfish stayed very close to the octopus despite two divers with cameras showing much interest for several minutes.
(As an aside, image 3 includes my buddy, who was kindly assisting me, refreshing my awareness of the important basics of buddy diving, as a prearranged mutual part of our dive plan. I'd been doing mostly solo dives at relatively safe sites like this,for so long, that I realised I might have become a potential liability for future buddies:)
I presume it was getting scraps from whatever the Southern Keeled Octopus has been eating, scavenging little crustaceans worms and molluscs disturbed by the cephalopod,or both.

Hopefully I got this right.4 Pics(all slide scans) from one or 2 dives at same spot. All(Editing:-debatable in images 2 and 3 ,which I should not have included, but as they show the general habitat I'll leave them in) include at least some bits of Macrocystis but with only the 1st being exclusively that genus. In the 4th,the back-lit fronds above the purple wrasse are Macrocystis. From memory Cape Jaffa had the most westerly outlier of giant kelp known at that time in SA. Plenty of bull kelp and other large canopy browns at that very high energy dive site but some of these plants were far longer,and distinctive indeed when the very long main axes streamed back and forth in swells. There were only small 'patches' of it,so I'd not be surprised to learn its locally extinct by now(thinking about the Tasmanian east coast scenario). Presumably M angustifolia. [Old slide scan image.Date approximate and for later editing per dive logs]

Typical line-up of adult Old Wives. On rising tide and when in relatively open areas, where predation risk is higher, they probably adopt these formations as a defence strategy. (I've previously speculated in detail on this topic, in an old MLSSA journal article, FWIW).

The same individual that I photographed on my last dive at Rapid Bay jetty, almost certainly. And after seeing it again on today's dive, behaving rather warily, after a short interval it reappeared coming fast in my direction, with a freshly captured Blackspotted Wrasse prey in its mouth. It was being followed by several decent size wrasses including at least one male Brownspotted, but the happy harlequin vanished into a hidden den where it presumably consumed its meal at leisure. I also noticed the female Striped Sea Louse on the Harlequin Fish, a sign of the times it would seem.

We've still got a veritable plague of these resident on the property and they mostly concentrate their burrows and runs around the periphery of the one poorly maintained but auto irrigated lawn. However nearby human residents continue to report good numbers of these native rats, and the rear slope of the North Dunes continues to support a large population. This large male approached me quite boldly while I was seated in a plastic chair on the lawn, and it was clearly inquisitive, not unaware of my presence.

Tentative at species level but undoubtedly the correct genus. Image 1 is cropped from Image 2(RHS),which explains the very limited image quality!
Snorkel from rocks at Bull Ring Bay.
Although not unexpected, I found it interesting that an adult Stigmatopora genus Pipefish was rafting aka hitch-hiking on a drift Posidonia blade so far from the mainland.
I also believe this is a Gulf Pipefish, whose common name would be inappropriate in the context of this observation, but that's just nitpicking by yours truly:)

With a Western Cleaner Clingfish on its flank. The subject appears to have displaced the magpie perch from the WCC sponge station. The subject is quite small and I don't know whether it is a juvenile or has reached reproductive stage. I'll punt on small adult.
Dodge tide, good conditions, nice dive.
I saw no Syngnathids, FTR.

Swanny Armina, found on the underside of a Sea Pen. Photo taken by my dive buddy Dennis Hutson (I didn't have my camera to take a shot, however I did observe this sea slug, as I was helping with photography- I hovered next to Dennis holding my torch light on subject). Photo was taken at 15m, about 10m away from a main structure; over sandy patch, with a small weedy/rocky patch. The sea slug was originally on the underside of the sea pen, it inadvertently dislodged, we waited a minute as it moved across some structure, which is where the photos were taken (right next to the sea pen). Size was approx; length 40mm, very wide, maybe 30mm (before it stretched out and started moving). Dennis noted he has NEVER seen one before in >25 years diving. my first obs as well. :)

With a hint of hybridisation with Bluethroat Wrasse, I suspect?
This mature individual was resting patiently in the ideal position for it to get a look at the 2 snorkellers (buddy and me) as soon as we'd entered the water on outgoing tide in near perfect conditions. It was on the shoreward aspect of the small rock pinnacle seen in the last image (included to viewers understand the habitat at this popular shore entry snorkel site, that photo was taken a few minutes before I entered and was taken from the exact entry point).Depth at pinnacle base was around 5m at this stage but at time of exit had dropped about half to 1 metre. Not drastic, but I mention it because the water clarity usually declines disproportionately as the tide here recedes.
Even on calm days with low swell forecast and actual, the cliff base is sufficiently shallow for small reduction in depth to magnify those swells greatly. One must wait for gaps between swell sets to make a safe exit at low tide,.Forewarned is forearmed as the saying goes. But the location is worth the effort, with the fish numbers and possibly diversity having already increased since the cliffs became part of this Green Sanctuary Zone. Average size of the various Wrasse species and even the two main sweep species has definitely increased also.

Collected under permit yesterday afternoon by hand during shallow intertidal snorkel in rock channel at Cape Jervis. Underwater photos of it as found crawling on fucoid brown algae have been added and were taken in natural light [This housed camera's flash often fires but does NOT illuminate subjects, unless I attach external strobe(s) which I didn't do on this snorkel] .

NB: I rarely collect invertebrates under permit, usually fish (and not nearly as often as I could given the opportunities that so often present ie small benthic fish which I don't recognize taxonomically with any confidence).

This slug is one I've never seen before, as far as I'm aware. I certainly don't have any images of one like this although it could be a colour morph of a described, even common taxon.
At first glance I thought it was a small dull blue to purple sponge aligned along the algal axis but I soon realized it was mobile, with gills at rear and rhinophores at front. I saw no sponges resembling it on this snorkel but it reminds me of a common type of sponge (possibly Callyspongia ) we often see at numerous locations in South Australia including the immediate vicinity albeit usually in the subtidal not intertidal.
Tide was incoming during the snorkel. I searched carefully for any other nudibranchs of similar appearance, to no avail.

Jetty dive. Common species in sea-grass but individuals seldom show themselves fully.

*Editing on 17-07-2021:
As flagged below in comments I agree that I've inadvertently included female(s) and male(s) in the one observation. I think it best not to backtrack/edit this too much or the comment trail loses meaning.
But I intend deleting image 3 asap (unable just now, not sure why:), especially as I've just used it as a new 'single photo' submission.
I can justify this action partly by noting the significant time gap of almost 30 minutes between the observations despite all images being taken during the same dive.
Sorry for making hard work of this!

Images supplied with consent to post on inat. Supplied by a resident whose house is on the rear slope of the secondary dune and very close to my residence.
Images taken in broad daylight and the resident photographer sees these rats in his garden during the day whenever he is home. That's been the case for many months now, prior to which he rarely saw rats diurnally on his property, and prior to which he could walk anywhere in his garden without fear of injury due the entire garden area being riddled with shallow burrows and tunnels.

No THIS is interesting. Yabby remains found at the wetlands, along the bank at the back pond. I’ve thrown a few little traps out to try catch them if they’re in there, but I’ve only caught Hardyheads. I’m definitely going to continue to try around different spots and see what happens. Someone may have thrown pet yabbies in here.

Though the Leafy Seadragon is more obvious the Tubemouth is slightly nearer to camera and is @ centre of image.
The two fish seemed very friendly or interested in each other however both may have been at a cleaning station (no host apparent in image nor at the time during scuba dive)
Depth about 6m

Snorkel in Kaurna pool Lady Bay platform reef some months after dreadful black silt catchment outflows temporarily blanketed most of littoral zone in this lower energy corner of Yankalilla Bay
Depth half a metre or so
(Makes me wonder why the black headed zebrafish adult variants became evident around that time ,after I'd never seen anything like it for preceding half decade ,approx.)

FURTHER UPDATE:- Please see most recent comment(10-07-2018) by Amanda Hay.It now appears certain that the subject fish is Heteroclinus sp 6,aka Milward's Weedfish.
[NB:Perhaps I should put this edit as a comment in its correct chronological order i.e. it perhaps it should follow Ms Hay's most helpful comment of earlier today. But then many viewers might not scroll down that far, thus remain unaware of ID @ species level.Because Milward's Weedfish has( if I understand correctly) not yet recieved full taxonomic recognition, is awaiting official acceptance of its scientific description.Once its status as a discrete species within Heteroclinus is finalized iNat can include it as species rather than the present situation where the 'final ID' must stop at 'Heteroclinus genus'.

[*from here on my description notes are thus largely obsolete, but I'll leave them isq for now in case some find them of passing interest *]

Update/Significant Edit: Initially I posted only the 1st of these 3 pics,with the notation "Probably perspicillatus but head partly obscured.Nice color. Snorkel,shallow."
I really didn't think I'd any other pics of this fish from this snorkel,but guess what,I just found 2 more. Neither is 100% sharp WRT focus,but the head is in view in both!
Apologies for overlooking these additional photos.Whether the focal sharpness is sufficient to confidently ID to species level remains to be seen but I'll ask about that in Comments below...

I've decided to post this image again, with the SUBJECT now the Western Cleaner Clingfish on the midfield Zebrafish ,because the cropped version nicely shows one of these Zebrafish clients' tricks for gaining the host's attention. The Zebrafish with the WCC on it has altered its bands so they don't match up on L and R sides. This may also indicate a degree of tactile rapture related to the contact with the host, but whatever the basis, AFAIK this 'switching' from bilaterally symmetrical bars to asymmetric bars has only been documented when Zebrafish are being cleaned. (By a WCC in this case, but possibly they sometimes also do it when being cleaned by other hosts eg Rockpool Shrimp, juvenile Moonlighter and juvenile Pencil Weed Whiting).
*If anyone has photographic evidence of any client species other than Zebrafish presenting overt morphological asymmetry (L vs R) as a transient phenomenon specific to a client host interaction, I would greatly appreciate their contacting me, or simply posting their observations on inat.

I've just noticed that this Castelnau's Wrasse which was the Subject of an earlier submission from this dive is being cleaned by a young Pencil Weed-Whiting. So, the head up bobbing posture so often associated with this Wrasse species is also used as a client posture during cleaning. (Juvenile Pencil Weed Whiting are known facultative cleaner hosts, but are harder to capture in the act than eg Western Cleaner Clingfish which are effectively full time hosts, as far as is known).

I don't often see juvenile Scalyfin in cup sponges, FWIW.
And on close zooming I think there's a (probably also juvenile) Western Cleaner Clingfish at the scalyfin's gill slit.
Makes sense, as Scalyfin adults are known to use the services of WCCs, so juveniles would surely need the same.