The Coast Guard prohibits vessels from getting closer than 300m from where Kilauea volcano's lava oozes into the sea.
The agency had been allowing experienced boat operators to apply for a special licence to get closer up to 50m, but it stopped allowing those exceptions on Monday.
A woman in her twenties was transported to Honolulu in serious condition with a broken thigh bone. The other 22 people injured were treated for minor burns and scrapes, including 12 who were treated at a hospital in Hilo.
Moku Nui Lava Tours Captain Kanoa Jones, whose boat was not involved in Monday's incident at Kilauea volcano, said not running the tours would only withhold income from local restaurants and other businesses dependent on tourism.
“If we stop operating, it not only hurts us, it hurts the community,” Jones said.
The Coast Guard, state and local officials were investigating what happened.
Coast Guard spokesperson Petty Officer 3rd Class Matthew West coudn't say whether they would change their safety zone rules until they finished their investigation.
The county strictly limits access to the lava on land for safety reasons, making boat and helicopter tours the only options people have to witness volcanic spectacle in person.
The ocean and aerial tours each cost about $250 (R3306).
The restrictions have deterred many travellers from visiting the Big Island in general, and Puna near the volcano in particular.
Shane Turpin, the owner and captain of the vessel that was hit, said he never saw the explosion.
He and his tour group had been in the area for about 20 minutes making passes of the ocean entry about 450m - which is the length of five football fields - offshore, Turpin said.
He didn't observe “any major explosions,” so he navigated his vessel closer, to about 230m away from the lava. “As we were exiting the zone, all of a sudden everything around us exploded,” he said. “It was everywhere.”
The molten rock is coming from the Kilauea volcano. - AP/African News Agency