Difference between revisions of "Diving the Cape Peninsula and False Bay/MV Aster"
Revision as of 06:51, 6 January 2012
The dive site M.V. Aster is a recent wreck in the Hout Bay area on the Atlantic seaboard of the Cape Peninsula, near Cape Town in the Western Cape province of South Africa. It is easily accessible by a short boat trip, and the ship was prepared for diving before it was sunk.
The wreck's position is well protected from the south easterly wind, and the depth is conveniently suitable for advanced divers. It supports a large variety of marine life, and is structurally still fairly intact.
During the preparation of the ship for scuttling, the interior was stripped of most snags and contaminants, and some access holes were cut in bulkheads and topsides, and as a consequence, the wreck is relatively safe for penetration by suitably skilled and equipped divers. Most of the compartments have some opening to the outside, through which light can enter, and only a few compartments are truly dark. This makes it a very suitable site for wreck penetration training.
S34°03.891’ E018°20.955’ (Mast)
In the middle of the mouth of Hout Bay, near the wreck of the Katsu Maru, about 700m offshore, and just beyond the main traffic lane.
This site is in a Marine Protected Area (2004). A permit is required.
The 340 ton "MFV Aster" was a South African registered lobster fishing vessel which was prepared as a diver-friendly artificial reef by cleaning and cutting openings into the structure before scuttling. The Aster was scuttled in Hout Bay near the wreck of the Katzu Maru on 9th August 1997. It has been used as a training site for wreck penetration, and a general dive site for advanced divers.
Maximum depth is about 28m in the scour at the bow and stern at low tide. This may reach 30m at high spring tides. Average depth of the wreck is over 20m. The gunwale of the main deck is at about 24m at low tide, and the top of the mast is at about 9m depth.
Visibility will vary from poor to about as good as you will get in Cape Town. 20m is possible, but 10m is more likely on a fairly good day, and less than 5m is entirely possible. The wreck is on fine sand and the visibility is significantly affected by swell. Large or long period swell will keep particles in suspension near the bottom. There is virtually no silting on the exterior of the wreck, but the interior is heavily silted in quiet corners. Interior visibility will also depend on diver skill and equipment, and not only will clumsy finning stir up the bottom, but bubbles may disturb material from the deckhead, which will then sink and reduce visibility. This is unavoidable unless diving on a rebreather, so only the first diver of the day will get clean water, and then only on a good day. The deckhead particulates are not as bad as the silt though, so it is still important to maintain precise buoyancy control and avoid bumping into things.
The ship stands almost level, embedded in the flat bottom as if floating in sand. The bow points towards approximately 330° magnetic (northwest). There is deep scouring of the sand at the bow and stern, usually to about 28m maximum at low tide, but has been known to reach 30m on a high tide. The vessel is is essentially intact and still looks much like when it was afloat. The hull has a few holes cut in it, and the superstructure is intact except for the wheelhouse, which has lost its forward bulkhead and roof. The tripod mast at the break of the forecastle and the forecastle deck are also intact. There is a fairly large rectangular hatch just forward of the superstructure, leading to a hold, and a winch with drums at each side on the main deck under the wheelhouse, open forward and to starboard and accessible also through a hole cut in the port topsides.
The vessel is about 36m long and the beam is about 8m.
The Aster is marked on the charts at the same position as the Katsu Maru and both wrecks can be visited on the same dive. The layout shown on the map is reasonably accurate, as it is based on the GPS tracks round both wrecks on the same dive.
The interior is generally very open, with almost no clutter of wreckage, but there are deep piles of silt in places. The engine room is quite crowded, but is the most interesting compartment as it is full of engine and exhaust ducting. There is also a ladder and a small catwalk. There is a bit of light in most compartments except the after accommodation below the main deck, and a few small compartments in the forward and aft accommodation areas. Most doors are very narrow, about 600mm, which is rather tight for a large person. Some access holes and hatches are even slightly smaller, so it can be rather tight for a large diver or if you are carrying large cylinders.
Most compartments are not more than two compartments away from outside access, and most have a window or porthole admitting light from outside. As a result there are several 'through routes' possible where you can go in at one point and come out at another. Obviously someone will have to go back to recover the line, and if several divers have passed through the visibility will be poor.
General arrangement of the interior: (see the drawing, it is not altogether accurate, but is a useful guide)
Geology: Flat fine quartz sand bottom.
The site is exposed to south westerly swells, which are beam on to the wreck and can cause a strong surge. The site is usually at its best in summer but there are also occasional opportunities in autumn and winter. On rare occasions there may be no surge at all and visibility of over 20m. The light levels are also highly variable, and not directly related to the visibility, as on some days it can be quite dark due to a dirty upper layer, and still have good visibility, while at other times the visibility gets worse with depth, but can be quite light due to strong sunlight and clear upper water.
This is an area which sometimes has upwellings, caused by strong south easterly winds, resulting in cold clear water, which may develop a plankton bloom over a few days, which will reduce the visibility again.
Keep a lookout for times when the south west swell is low and short period, and there is not too much south easterly wind forecast.
Access is only reasonably practicable by boat. The site is about a 2.2km ride from the harbour slipway. The wreck is in the harbour approaches, and there may be significant boat traffic. Dive boats will usually drop a shotline with a large marker buoy. This is the best place to descend and ascend as the boat will remain nearby and this indicates to passing traffic that divers are on site and they will keep clear.
The wreck is heavily encrusted with common feather stars and sponges, with good representation by colonial ascidians and hydroids. The mast has urchins, black mussels and barnacles near the top. There is a fair range of other species, and the rarely sighted Tasselled nudibranch Kaloplocamus ramosus has been seen here several times. Large rock lobster lurk in the recesses, and rock crabs scuttle around amongst the encrustations of invertebrates. A few small kelp plants have established themselves on shallower parts of the wreck.
The Aster is a recent wreck in fairly intact condition. The structure is sound and apertures have been cut to make the wreck more diver-friendly for penetrations. Most of the structure is clearly recognisable, and all of the exterior is easily accessible for the advanced diver.
Much of the interior is accessible to competent wreck divers, depending on skill and equipment, and to some extent physical size. Penetrations of varying levels of difficulty are possible. The structure is fairly sound, and relatively uncomplicated.
Macro and/or wide angle equipment is recommended. Most of the time macro equipment will give the better results, but on a really good day you may get some fine wide angle shots. Macro will require flash.
No special route is recommended.
Hazards at this site are due to cold water, occasional fog, and boat traffic. There is also a danger of possible entrapment if the wreck is penetrated. Some of the structure may be unstable, and the superstructure has lost a few components. Strong surge is common if the swell is large or the period long, as the vessel lies directly across the prevailing swell direction and a strong surge will create severe turbulence over the weather side gunwale.
Penetration is relatively easy as the wreck was prepared for divers before sinking. However, not all divers will fit through all of the access openings, and this also depends on your rig. Bulky BCs, dangly hoses, big cylinders and long, hinged or split fins all provide a collection of things to get snagged.
It is quite possible for a group of divers to enter the wreck, and for only the smaller ones to be able to get out the chosen exit hole, so bigger divers may have to backtrack to get out.
No special skills are required unless penetration is intended. It is necessary to be qualified for 30m dives, so most "Advanced diver" certifications are appropriate.
Penetration is not recommended unless you are trained in the procedures and have suitable equipment. This being said, the Aster is a good wreck for wreck penetration training, as it is small, compact, and relatively snag-free, with an adequate number of access holes so that it is not likely to be more than three compartments from an exit.
A light will restore colour and allow you to look into the wreck. A reel and DSMB are worth carrying in case it is necessary to surface away from the shotline. A dry-suit is recommended as the water is usually quite cold, but many divers have dived the Aster in wet suits. Nitrox is recommended to extend no-decompression time.
Divers competent to plan and execute penetrations will know what additional equipment they will need. If you don't know, then stay out and stay alive, or attend a wreck diving training programme — there are several local schools offering the training.