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.
In the middle of the mouth of Hout Bay, near the wreck of the Katsu Maru, about 700 m offshore, and just beyond the main boat traffic lane from the harbour.
This site is in the Table Mountain National Park Marine Protected Area since 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 9 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 28 m in the scour at the bow and stern at low tide. This may reach 30 m at high spring tides. Average depth of the wreck is over 20 m. The gunwale of the main deck is at about 24 m at low tide, and the top of the mast is at about 9 m depth.
Visibility will vary from poor to about as good as you will get in Cape Town. 20 m is possible, but 10 m is more likely on a fairly good day, and less than 5 m 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, avoid bumping into things, and keep a level trim.
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 28 m maximum at low tide, but has been known to reach 30 m on a high tide. As of January 2017 the scour pits have filled in a lot and the rudder is almost completely under the sand. The vessel 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. Mussels grow preferentially at the side of the openings, where there is more water movement, and tend to close the access gaps. Divers do occasionally clear them away to improve access, but do not rely on this. These are probably the alien invasive Mediterranean mussels.
The vessel is about 36 m long and the beam is about 8 m.
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. There has been a lot of growth of Mediterranean mussels on the wreck around the edges of the openings, making them a bit smaller. some may be too small for the larger diver with back-mount cylinder, but the mussels can be removed without too much difficulty. There are also very large numbers of Cape sea urchins on the outside surfaces that aren't too steep for them.
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)
- The wheelhouse has lost its forward bulkhead and deckhead (roof), and is also now open to the captain's cabin behind it. These are totally open and accessible from outside, and do not constitute a penetration.
- The forward hold (Fish hold) has two rows of pillars supporting the deck. There is a large rectangular opening and a large more square hatchway with a raised coaming in the main deck providing direct access to the outside, and large access holes both forward and aft into other compartments at this level. The bulkhead between the fish hold and the offal room appears to have been removed and it is now a single large compartment. There is also a small square hatch to the main deck forward, but this is obstructed by invertebrate growth. Forward is the store, and aft is the engine room. Silt has built up on both sides of the hold.
- The store under the forecastle is accessible from the fish hold aft through a big cutout on both sides of the mast, through a compartment which has some machinery in the middle. There is also an adequately sized hatch through the main deck just forward of the base of the mast.
- The forecastle is accessible through a wide doorway in the aft bulkhead on the port side. The crew washroom door is just to the right as you go in. The crew washroom is very small, but the accommodation space is quite roomy. There is a small square hatch down into the chain locker that is too small for a diver wearing a cylinder.
- The engine room is accessible from the aft end of the Fish hold/Offal room space below the main deck and extends up through the superstructure where there are doors to other superstructure areas on both sides, and up behind the funnel where there was probably a set of skylights or ventilation hatches, where a fairly large access hole has been provided. The engine room is quite large, but relatively cramped due to the fuel oil wing tanks to port and starboard forward, the engine in the middle, the stack ducting above the engine, and the ladder and catwalk aft. The ladder is to port of the engine and leads up to a catwalk at main deck level, with a door to port leading to the aft accommodation spaces, which are all interlinked and have several access routes.
- on the starboard side there is access via very tight catwalks to the forward compartment on the starboard side below the wheelhouse.
- There is a fairly large compartment in the superstructure on the starboard side just aft of the winch area. This has a door to the main deck and has access to the engine room.
- The aft accommodation spaces in the superstructure can be reached from the engine room at the upper deck level by a doorway on the port side, through two doorways on the upper deck on the starboard side, through a hatchway from the bridgedeck, and through a cutout in the upper part of the transom. The hatch from the bridgedeck is fairly tight, and it may be too small for some divers. Light comes in through various portholes and rusted areas in the plating.
- The wide opening on the starboard side of the superstructure next to a ladder to the quarterdeck leads to a small compartment, with another door inboard. This leads into what was probably the crew's messroom. There are a number of small compartments leading off this space. On the port side forward is what may have been an office or the engineer's cabin. It is close to a door to the engine room, and there is an opening in the deckhead into the wheelhouse above. Aft of this is a small compartment without windows, which may have been a store or very small office.
- Aft of the entry on the starboard side there is another small compartment, containing a hatchway down to the sleeping quarters, and with a skylight above. The hatchway down is fairly big (big enough for a 1.8 m, 90 kg diver with a single 15 litre cylinder on a backplate and a small bailout cylinder, but a close fit), but the space below is very dark, and a light is absolutely necessary. The accommodation space is virtually empty, but there is a lot of silt on the deck. There is a second access hatch central on the aft bulkhead, which is smaller than the forward hatch, and accessed through a small tight compartment with a narrow door on the main accommodation deck.
- Behind the wide door on the starboard side there is a small store opening only to the upper deck, and then a door to the upper deck at the extreme aft end of the narrow side deck on main deck level, under the quarterdeck.
- More or less central at the aft end of the messroom there is a small alleyway leading to a compartment across the transom, where a large opening has been cut for diver access.
- On the starboard side there is a narrow compartment running fore and aft. Inboard of that is a small toilet compartment (heads), athwartships.
- On the port side is a small empty compartment, possibly a store.
- On the port side just forward of this space there is another small compartment, possibly a store, with a small hatch giving access to the steering compartment. The hatch looks too small for a diver wearing a back mounted set, and forward of that, with a door facing forward, another small compartment.
- Forward and slightly outboard of that is another small compartment with a door facing forward.
- To starboard of the alleyway, opposite the compartment with the hatch down to the steering compartment, there is a very narrow compartment with a hatchway leading down into the aft accommodation in the lower part of the hull. This hatchway is very small and probably too tight for most divers while wearing a back mount cylinder and buoyancy compensator. Only divers with side-mount equipment and the requisite skills should consider penetrating this compartment, but if you stick your light down the hatch you will be able to take a look inside. This compartment is the same one that is accessed by the larger hatch further forward.
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 2.2 km 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 among the encrustations of invertebrates. A few small kelp plants have established themselves on shallower parts of the wreck. As of 2017 the population of the invasive alien Mediterranean mussels has exploded, and so have the Cape urchins and fragile brittlestars, at the cost of most other invertebrates. The mussels are partly obstructing some of the openings into 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.
- Start deep and progress upward. The wreck is small enough to swim around on a single dive if you just want to see the view. Start wherever convenient, and visit the scour pits at the propeller aperture and bow if you want to record maximum depth. Then ascend to the top of the hull on either side and swim around it at the depth of the gunwale, visiting the main deck and break of the forecastle as excursions. Finish the dive on the shallower parts on the superstructure, or work your way up the mast if not using a SMB or shotline.
- If you wish to visit the Katsu Maru, swim to the southwest from the middle of the port side of the Aster, perpendicular to the length axis of the Aster. It is about 30m away — too far to see even on a good day — but a large enough target to find quite easily if you are moderately skilled at navigation. To return, find the wheelhouse of the Katsu Maru, swim over the hull to the keel, and swim away perpendicular to the line of the keel.
- Penetration is possible if the surge is not too strong, but should not be attempted by divers without appropriate training and equipment. It is a good idea to scout the proposed route from outside first and check that the exit hole will be big enough for you and your equipment. There are plenty of convenient tie-off points near the access openings.
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 30 m 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.