BLACKMARK - Southern Islands

Blackmark is one of our favourites in the Southern Islands, not because it’s a giant wreck, but because of its character. This old ferro-concrete workboat, sunk back in ‘80, rests upright in about 11 metres of water. It’s pretty compact, maybe 15 metres end-to-end, but what it lacks in size it makes up for in how it’s aged. We always find something new here. The concrete hull has become a canvas for soft corals, particularly a striking orange cup coral that blooms in the darker sections. On a sunny day, with decent visibility, you can really appreciate the colour. Inside the open hold, we often spot robust ghost pipefish swaying with the surge, nearly invisible against the encrusted walls. Look closely for nudibranchs, especially on the propeller shaft. It’s a gentle dive, perfect for photographers or anyone wanting to spend time exploring the nooks and crannies of a unique artificial reef. Just keep an eye on the tide; the currents here can pick up, making it a bit more of a workout than you might expect for such a shallow spot. We usually aim for slack high tide for the clearest water and easiest conditions.

Location
Southern Islands, Singapore, Southeast Asia
Coordinates
1.250000, 103.848335
Type
wreck
Maximum Depth
11m

Wreck History - BLACKMARK

Year Sunk
1980
Vessel Type
cargo ship
Cause
unknown

The "Blackmark" was a highly unusual vessel: a roll-on/roll-off work boat constructed from ferro-concrete. This building method, which uses a steel mesh frame covered in concrete, was a rare and often experimental alternative to traditional steel hulls. On January 3, 1980, this unique boat sank for undocumented reasons in the busy waters near Singapore's Southern Islands, a popular area for local shipping and recreation.

Now lying at a shallow 11 meters, the Blackmark presents an intriguing but cautious dive. It is officially designated as a "Dangerous Wreck," likely due to hazards such as sharp, rusting rebar protruding from the decaying concrete hull, entanglement risks, and potential structural instability. For experienced divers who are properly equipped and mindful of the dangers, the wreck offers a rare opportunity to see a ferro-concrete ship up close and observe how this unconventional material has weathered decades on the seabed.

Marine Protected Area: Labrador Nature Reserve

Best Time to Dive in Southern Islands

The warmest water temperatures in Southern Islands occur in January, averaging 28.2°C. The coolest conditions are in December at 28.2°C.

Monthly Water Temperatures

  • January: 28.2°C (air: 26.0°C)
  • February: 28.2°C (air: 26.6°C)
  • March: 28.2°C (air: 27.1°C)
  • April: 28.2°C (air: 27.4°C)
  • May: 28.2°C (air: 27.9°C)
  • June: 28.2°C (air: 27.4°C)
  • July: 28.2°C (air: 27.5°C)
  • August: 28.2°C (air: 27.2°C)
  • September: 28.2°C (air: 27.2°C)
  • October: 28.2°C (air: 27.2°C)
  • November: 28.2°C (air: 26.5°C)
  • December: 28.2°C (air: 26.3°C)

Nearby Dive Sites in Southern Islands

Nearest Dive Centres to BLACKMARK

Marine Life in Southern Islands

Home to 284 recorded species including 179 reef fish, 46 hard corals, 17 seagrass & algae, 13 sharks & rays, 8 sea snails & nudibranchs, 6 other.

Notable Species

Recommended Packing List for BLACKMARK

Based on average water temperature of 28.2°C.

  • Shorty or Rashguard - warm 28°C water needs minimal exposure protection
  • Mask - essential for every dive
  • Fins
  • BCD - buoyancy compensator
  • Regulator - your most safety-critical piece of gear
  • Dive Computer - tracks depth, time, and NDL
  • Surface Marker Buoy (SMB) - essential for boat pickups
  • Dive Torch - useful for crevices and colour at depth
  • Underwater Camera - capture your diving memories