The lava bomb or a flying chunk of molten rock, punctured the boat's roof on Monday after which it returned to Wailoa Harbour, CNN quoted the Hawaii County Fire Department as saying.
Of the injured, one woman in her 20s was in serious condition with a fractured femur.
It was unclear exactly where or when the incident occurred. But from where lava from the Kilauea volcano is hitting the ocean to the harbour is about an hour's boat ride, depending on waves.
Kilauea erupted in early May, sending a smouldering flow of lava into residential areas on the Big Island.
Kilauea was still erupting lava as of Sunday, according to the US Geological Survey (USGS).
Meanwhile, the lava has also created a tiny new island off the coast of Hawaii.
The island is part of the lava flow that extends underwater away from the coastline, according to the USGS.
If the lava flow stays active, the island will probably connect to the coastline. If not, it might erode away because of wave action.
The agency said the island is just a few metres offshore, and about 20 to 30 feet in diameter.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
