The dive site '''Blue Rock Quarry''' is a disused quarry. It is the only significant fresh water dive site with public access in the greater metropolitan area of Cape Town in the Western Cape province of South Africa.
The site is diveable in all weather conditions, and provides a large range of depths, and is useful for training and familiarization with equipment and procedures.
[[Image:Blue_Rock_Quarry.png|400px|thumb|Chart of the Blue Rock Quarry showing 10m and 20m contours and a few spot depths. The red line indicates the overhead ski tow cable.]]
===Access=== Take the turnoff to the north to Sir Lowry’s Pass village from the N2 at the Gordon’s Bay turnoff at the foot of Sir Lowry’s Pass. A few hundred metres along there is a turnoff to the left to a short access road which runs more or less parallel to the main road. Turn into the gate to the left and pass through the security gate. The gatekeeper will require payment of the entry fee. Drive along the tar road and further along the dirt road until you reach the parking area near the buildings. An entrance fee of R30 and a charge of R80.00 for diving is levied per person for the day (Sept 2009). Parking is usually adequate but equipment will have to be carried about 50m to the water. Adequate paths and stairs are provided near the buildings, and old access roads provide safe access to the water at two other places. Enquire at the shop about vehicle access to these roads. Four wheel drive, differential lock and reasonably high ground clearance recommended.
There are three areas usually used for diving access. #The platform where the water-skiers launch, at the bottom of a set of stairs in front of the buildings. There is an adequate set of steps at the east end of the jetty for getting out. #The shore at the west end, where there is easy access at the base of the north western pylon. #The old access road at the south east corner. There are a couple of containers and diving compressors which belong to a commercial diving school who use the site several days per week for surface supplied diver training . The area is not owned by the school, and recreational divers may use the access when the school is not using it. If the school has a diving operation under way the supervisor will not generally allow recreational diving on the site under his control. Do not push your luck, the supervisor is legally empowered, by the Occupational Health and Safety Act and the Diving Regulations, to have any person who in his opinion may interfere with or compromise the safety of the diving operation removed from the site. His opinion, not yours. The commercial schools do not usually work on weekends. [[Image:(view of the site and facilities)|thumb|View of the Blue Rock Quarry looking west from the road near the access gate. ]]
This site is NOT in a Marine Protected Area
The "Blue Rock Quarry" was named for the building aggregate which was quarried there in the past, which was a dark blue-grey colour. The quarry was closed and is now flooded and used for water sports including diving.
The bottom is stepped, except at the old access roads. The level at the west end and the west part of the south and north sides is at about 10m, then drops almost vertically to about 20m, then further east it drops off again more gradually over a boulder slope to the main level at about 25 to 30m.
The East end is deeper, from 30 to 40m in most places, and the deep area in the south east corner extends to at least 47m, though there are unconfirmed reports of greater depth.
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The sides of the quarry are almost sheer rocky walls, with loose boulders and occasional slight overhangs. Care must be taken not to dislodge rocks when divers may be below. The bottom is very silty and visibility is badly affected if it is disturbed.
An old access road at far side (north west corner) winds down the side of the quarry below the water.
(views of the entry point)|thumb|View from the south east corner. The deep end is to the right of the photo. The old access road in the north west corner can be seen in the left background.]]
The east end is deepest and exceeds 40m in places. Maximum depth is claimed to be over 60m in a very small area.
The west end is shallower and stepped down to a flattish silty bottom at about 25m. There are large and small boulders scattered on the bottom and everything is covered by fine silt. There are submerged trees in places, mostly along the sides where the slope is not too steep, like on the old access roads. These could cause entanglement of divers equipment and due care should be taken to avoid this. There is some debris left from the quarry operators, and from the builders of the ski-tow system, and some dive schools have permanent training aids on the bottom. These should not be moved or vandalised.
Three permanent shotlines are sited in the south east corner and are property of a commercial diving school.
The quarry was a commercial source of Cape Blue Rock, a dense Hornfels, (fine textured contact altered argillaceous [from clay] rocks) from the Pre-Cambrian ''Malmesbury'' series. The Hornfels was formed when the nearby Stellenbosch granite pluton intruded more than 530 million years ago.
This is an area which sometimes has a noticeable thermocline, and the depth can vary with the seasons, being deepest at the end of summer, when it may be between 8 and 15m.
(view of the site and facilities)|thumb| The The restaurant and offices are in these buildings . This view is from the parking area . Access to the water is to the right of the buildings down a paved staircase to the dock.]]
Parking is adequate, and security probably not bad.
Toilets and changing rooms are available, and a fast-food restourant may be open.
Overhead ski-tow facilities are the main feature at this site, and may present a hazard to divers. However, as this is the main attraction, complaints will probably be a waste of breath. Keep clear of the ski zone and you will be OK, or dive on a Monday, when the ski-tow is closed.
There are small fish, freshwater crabs, Platannas (African clawed toad) and some larger fish which have not been identified, but may be carp. Small fresh-water jellyfish have been seen at some times of the year, but have not been reported recently.
Not recommended for photograpc enthusiasts as there is little to photograph, and the visibility is usually poor and the water dark.
#Multi level dives are easily made near where the road enters the water. The road can be followed, or by swimming at right angles to the road, the depth increases in steps to about 25m at the west end. Take care to keep clear of the water ski route under the cable system when near the surface.
#Deep dives can be done using the moorings of the rafts as shotlines, or for greater depth shotlines can be set up to suit the dive plan. If it is expected to obstruct the ski zone, be sure to make arrangements with the management ahead of time. There are
three permanent shotlines belonging to the commercial diving school, which may be used if they are not operating on site.
Poor visibility in the rainy season, or when the silt is disturbed by divers. Nitrogen narcosis in deep areas, Loose rocks on walls, Submerged trees and possibly other debris. Water skiers under the towline.
Very suitable for training. No special skills required. The West end is relatively shallow and there are few submerged trees. For shallow water training exercises the submerged access road in the north west corner is suitable.
If doing deep dives, the gas may be chosen to suit the planned profile, and a light, reel and dsmb are recommended.
Back to [[Diving the Cape Peninsula and False Bay]]