Diving the Cape Peninsula and False Bay/SAS Bloemfontein

The dive site SAS Bloemfontein is a deep recent wreck in the central part of False Bay, near Cape Town in the Western Cape province of South Africa.

Understand

The wreck is in quite good condition for its age due to the depth.

Type: Algerine-class minesweeper

Displacement: 965 t (standard)
Length over all: 68.6 m
Beam: 10.8 m
Draught: 3.7 m
Installed power: 2 × Admiralty 3-drum boilers
Propulsion: 2 shafts, 2 vertical triple-expansion steam engines, 1,800 kW
Speed: 16.5 knots (30.6 km/h)
Range: 5,000 nmi (9,300 km) at 10 knots (19 km/h)
Complement: 85
Armament:
- 1 × QF 4 in (102 mm) Mk V dual purpose gun
- 2 × twin and 2 × single Oerlikon 20 mm AA guns

HMSAS Bloemfontein was an Algerine-class minesweeper built for the Royal Navy in Canada during World War II. The ship was originally named HMS Rosamund (pennant number: J439) and spent several years clearing minefields in Europe after she was completed in 1945 before she was placed in reserve. Rosamund was purchased by South Africa in 1947 and renamed.

The ship spent most of its early career in the South African Navy training or making good-will visits to foreign countries. She was laid up in the late 1950s and was recommissioned in 1961 to serve as an interim training ship until the shore-based training establishment then under construction was completed. This occurred in 1963 and Bloemfontein briefly returned to reserve before she was deemed surplus to requirements. The ship was sunk as a target in 1967.

Position

S34°14.668’ E018°39.974’ SAS Bloemfontein wreck 📍 (approximately amidships) This is right in the middle of False Bay.

This site is NOT in a Marine Protected Area. A permit is not required.

Name

The "SAS Bloemfontein" M439 was a sister ship to the SAS Pietermaritzburg and has similar dimensions and layout. This Algerine–class Minesweeper was built as HMS Rosamund, and was scuttled on 5th June 1967.

Depth

Maximum depth is about 55 m in the scour depressions in the sand at the bow and stern. The upper deck is at about 47 m.

Visibility

Visibility is not easily predictable. Surface conditions do not necessarily indicate visibility at depth. The surface may be cloudy from plankton, and it may improve below the plankton layer, but can also get much worse near the bottom, where there may be a layer of very poor visibility for the last few metres. This may be a characteristic of deeper False Bay waters in winter, but there is not enough data available to analyse.

Topography

The ship lies upright on a flat sand bottom with the bow to the northwest, and is substantially intact. The stern area is in relatively good condition, the rudder and shaft brackets are intact and there are a number of interesting details visible on deck and inside the hull. In several places plating has wasted through and the interior is visible. Scour pits at bow and stern are seasonal.

Geology: Flat shelly sand bottom.

Conditions

The site is in the middle of False Bay, and is affected by wind and waves from all directions, so can be dived only on the rare occasions when there is very little swell or wind, as the bottom time will be short and this is almost always a decompression dive. Due to the depth the surge is greatly affected by wave period, with short period swells having little effect at the bottom, while longer periods will reach all the way down. Wind chop will have little effect at the bottom, but may make the surface conditions unpleasant or hazardous, and the trip to the site and back is long and will be uncomfortable in steep waves or strong wind.

This is an area which often has a significant variation in temperature between the surface and bottom waters, and sometimes a distinct thermocline, particularly in summer. In winter it is more likely to be only a few degrees difference top to bottom, with no sharp thermocline.

Keep a lookout for times when the sea is flat, the visibility is good and the wind is light. If the wind comes up during a dive, you just have to live with it, so check the forecast on the day.

Get in

Only accessible by boat. This site is a similar distance from Simon's Town jetty (22 km), Gordon's Bay Old Harbour (20 km), Kalk Bay (24 km) or Miller's Point slipway (18 km), and it is a matter of convenience which is used. The wreck is not easy to find and the boat should have at least a serviceable echo-sounder and GPS.

See

Marine life

The structure is not heavily encrusted, bur has a lot of short brown growth, probably mostly small colonial hydroids, and a scattering of sea fans, oysters, strawberry anemones, encrusting sponges, and rock lobster.

Features

Steel shipwreck of World War 2 vintage.

Photography

The marine life is not very diverse, so not much of a site for macro. If you are lucky and have a day with good visibility and natural lighting, a fisheye lens for close up wide angle views of the structure is likely to give the most satisfactory results.

Suggested Routes

No particular routes recommended. It is possible to swim around the perimeter of the wreck in 15 minutes.

Stay safe

Hazards

Cold water possible. Strong winds may develop over a short time. Nitrogen narcosis is likely on air or Nitrox.

Skills

Only suitable for divers who have the training, skills and equipment to dive deeper than 50 m. Penetrations should only be planned by suitably competent divers who have dived the site recently and assessed the condition of the structure, as it is deteriorating and the stability is questionable.

Equipment

The dive has been done on air in the past, but appropriate gas mixes are strongly recommended to improve safety and reduce decompression time. Lights are strongly recommended as it is usually fairly dark at these depths. DSMB and spool should be carried by each diver in case of ascent off the shotline. You do not want to get lost on this site, and if the wind comes up the SMB will help the skipper keep track of you.

Nearby

Other offshore dive sites of False Bay:

Back to the Alphabetical list of sites, or list of wreck dive sites in the False Bay offshore area

Other regional dive sites:

Related Wikipedia article: HMSAS Bloemfontein