BIG SEA 5 - Koh Tao

Big Sea 5. We love a good wreck, especially one with a story, and this tanker delivers. She’s the old Masayoshi Maru No 2, a good-sized vessel at nearly 70 metres, now resting upright at 30m. Dropping down, you’ll first see the superstructure, a dark silhouette against the blue, before the details emerge. We always head for the bridge first, imagining the helmsman’s last view. Her holds are open, inviting you inside. It's dark in there, so good lights are essential, and a reel is smart if you’re venturing deep. You’ll feel the subtle shift in temperature as you penetrate, and the sound of your own bubbles echoes around you. Schools of fusiliers often swirl just outside the openings, flashing silver as they catch the light. Look for barracuda patrolling the deck, their eyes following your every move. We’ve spotted large groupers lurking in the shadows of the engine room. It’s a proper wreck dive, perfect for those comfortable with deeper profiles and a bit of overhead environment exploration.

Location
Koh Tao, Thailand, Southeast Asia
Coordinates
11.900000, 100.336830
Type
wreck
Maximum Depth
30m

Wreck History - BIG SEA 5

Year Sunk
2003
Vessel Type
tanker
Cause
scuttled
Tonnage
730 GRT

The vessel now known as the Big Sea 5 began its life in Japan in 1982, christened the Masayoshi Maru No. 2. This 70-meter coastal tanker spent years transporting fuels and other liquids before being sold to the Big Sea Co Ltd in Bangkok, Thailand, and renamed. As the Big Sea 5, it continued its service in the bustling shipping lanes of Southeast Asia, a reliable workhorse of maritime industry.

After a long and productive career, the tanker was retired. Rather than being sent to the scrapyard, it was given a new purpose. In 2003, the Big Sea 5 was thoroughly cleaned and prepared before being intentionally scuttled off the coast of Koh Tao. This sinking was part of a project to create a new artificial reef, aimed at relieving pressure on natural dive sites and providing an exciting new underwater attraction for the island's thriving dive community.

Resting upright on the seabed at a maximum depth of 30 meters, the Big Sea 5 is a fantastic wreck dive for advanced divers. The ship is largely intact, allowing for exploration of its deck, superstructure, and bridge. Over the years, it has been beautifully colonized by marine life. Large groupers and barracuda are often seen patrolling the wreck, while dense schools of fusiliers and snappers swarm around its highest points. The wreck's size and depth make it a rewarding and atmospheric dive, a perfect example of a vessel's successful transformation from industrial workhorse to vibrant marine habitat.

Marine Protected Area: Khao Sam Roi Yot Wetland

Best Time to Dive in Koh Tao

The warmest water temperatures in Koh Tao occur in May, averaging 30.6°C. The coolest conditions are in January at 28.3°C.

Monthly Water Temperatures

  • January: 28.3°C
  • February: 28.6°C
  • March: 29.3°C
  • April: 30.2°C
  • May: 30.6°C
  • June: 30.2°C
  • July: 30.0°C
  • August: 29.7°C
  • September: 29.4°C
  • October: 29.2°C
  • November: 29.3°C
  • December: 28.6°C

Nearby Dive Sites in Koh Tao

Nearest Dive Centres to BIG SEA 5

Marine Life in Koh Tao

Home to 56 recorded species including 35 reef fish, 11 sharks & rays, 4 other, 2 hard corals, 1 clams & mussels, 1 sea urchins.

Notable Species

Recommended Packing List for BIG SEA 5

Based on average water temperature of 29.5°C, currents 14 cm/s.

  • Shorty or Rashguard - warm 29°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