It was one month ago that 220,000 gallons of molasses leaked into Honolulu Harbor through a broken pipe owned by Matson.
The molasses spill killed 26,000 fish. The Sierra Club-Hawaii Chapter deemed the spill one of the worst environmental disasters in state history.
State and federal officials are still investigating the leak to determine the extent of the damage at Honolulu Harbor and Keehi Lagoon.
Divers took samples of coral, sand and mud from the bottom of the ocean floor yesterday.
Earlier dives showed much of the reef had died but water quality readings are back to normal.
Taxpayers have paid millions of dollars to clean up the spill and dead fish, and are now funding the investigation and monitoring.
Matson faces steep fines from federal and state agencies, and could be forced to pay part or all of the clean up costs.
More than 1,500 Sierra Club members have asked lawmakers to ensure Matson is held accountable for its actions, but so far lawmakers have not held hearings on the spill.