The section of Sydney's coastline that is relatively undived is the area between Botany Bay and Sydney Harbour. Apart from just south of the Harbour on South Head, the Magic Point Sharks and a couple of shore dives like Shark Point and North Bondi, there is no visitation by dive charter operators. This is a pity as there are literally hundreds of great dive sites here.
Just south of the Magic Point grey nurse shark site at South Maroubra there are quite a few great dive sites. This is behind the Long Bay Rifle Range and the coast here is relatively untouched by man. Until the early 1990s, the Malabar Sewage Treatment Works poured basically untreated shit into the water at Yellow Rock, the southern-most point of this section of coast. However, once the deep-water outfall was opened and the treatment works upgraded to secondary treatment, the water cleaned up so dramatically it was amazing.
Before these works, the sponges and kelp all over this area (if you were brave enough to dive here) were all stunted. Within a few months the environment started to improve, with the sponges and sea squirts growing to normal size and the kelp coming back to be lush and all covering.
In the mid to late 1990s we did a number of dives along the rifle range. We found some great sites, including Red Flag, the Ladder and Yellow Rock. However, apart from a couple of dives in 2002 and 2004, I had not dived this area again till late 2009.
From Botany Bay, turn left as you exit the heads and run towards the north. Go past Little Bay and Long Bay and just after you pass the outer northern headland of Long Bay, run in close to the shore with your depth sounder on. You will see that this whole section of the coastline has a really great bottom. There are a number of walls here, all roughly running north-south.
Go to GPS S33ΒΊ 57' 59.3" E151ΒΊ 15' 55.8" (all my diving GPS co-ordinates use AUS66 datum - read my GPS page if you do not know what this means). Run in towards the shore and drop anchor when the depth comes up from 24 metres or so to about 18 metres.
Once on the bottom, you will see that there is a wall that drops from about 20 metres to 24 metres. This wall weaves around a bit, sometimes going north-south but other times in towards the shore for a few metres. Once at the deeper wall, drop down and head north. Along this section there are some large rocks/boulders off the wall, with some sea dragons hanging around the kelp.
After about 100 metres there are some very large boulders on the wall area and in good visibility, you will be able to seen another wall that goes from about 10 metres to 15 metres. In between the two walls the bottom generally slopes and is a rocky bottom. These boulders have some overhangs and swim-throughs. There are also a lot of fishlife in between them. The fish are generally ladder-finned pomfrets, yellowtail and seapike, with some one-pot pullers. There can be thousands of the pomfrets and they make a spectacular sight.
This is a good spot to turn around. Come back at the bottom of the shallower wall, in the 15 to 17 metre range. Again, there are some small overhangs in the main wall and you can get eastern blue devilfish, cuttlefish and the normal cave dwelling fish here.
Once back at the anchor, head south for about 50 metres and then out to the deeper wall. Follow this back to the north to the anchor. You will probably still have a few minutes left to hang around the anchor before you need to ascend.
This is an excellent dive site, it is a pity that you can only dive here if you have your own boat.