The Coast Guard warned charter tour operators and private boaters to keep a safe distance from the Kilauea volcano lava flow entering the sea on Hawaii’s Big Island.

It is the second time in little more than a year that the Coast Guard has policed spectators edging in for a look at Kilauea flows. This time the molten rock is grinding its way offshore in the Mackenzie State Park Lower Puna region.

“For mariners without prior limited entry approval, the safety zone encompasses all waters extending 300 meters (984 feet) in all directions around the entry of the lava flow into the ocean,” said Lt. Cmdr. John Bannon, the Coast Guard Sector Honolulu waterways management lead. “All waterway users should be aware of the hazardous conditions associated with such an event. Getting too close to the lava can result in serious injury or death.”

The ocean entry poses its own danger in the form of laze, steam clouds containing hydrochloric acid and fine glass particles that erupt as lava hits seawater, according to Hawaii Civil Defense officials. That can cause lung, eye, and skin irritation and damage.

Earthquakes, new lava deltas and cliff collapses add to danger at the shoreline, Coast Guard officials said. The 300-meter safety zone is based on decades of U.S. Geologic Survey volcano observations of how lava and ejected rock behave during eruptions.

Restrictions around the Lower Puna safety zone began at 8 a.m. Sunday.

Contributing Editor Kirk Moore was a reporter for the Asbury Park Press for over 30 years before joining WorkBoat in 2015. He wrote several award-winning stories on marine, environmental, coastal and military issues that helped drive federal and state government policy changes. He has also been an editor for WorkBoat’s sister publication, National Fisherman, for over 25 years. Moore was awarded the Online News Association 2011 Knight Award for Public Service for the “Barnegat Bay Under Stress,” 2010 series that led to the New Jersey state government’s restoration plan. He lives in West Creek, N.J.