There are several sites in this area around Sandfly Island. At the south eastern entrance there is a wall drift with lots of fans with quite a few exceeding 3 metres in diameter. On the southern side, approaching the passage, is Robert's Point or Baracuda Point. Robert is the local Chief here - nice fellow and good for a yarn.
Twin Tunnels, close to Tulagi, is a coral bombie approximately 120 metres in diameter. The top of the reef is in 12 -16 metres of water and features two tunnels eroded in the edge of the reef descending down to a common cavern exiting to the wall at 35 - 40 metres.
The top of the reef is spectacular in its own right and there is no need to go down to the cave. Many divers enjoy the thrill of going down one or other of the tunnels though.