The source of the lava was Kilauea, one of the world’s most active volcanoes, which has attracted tourists in recent months who are eager to see the piping hot rock for themselves.

After the episode, all vessels were restricted from traveling within 300 meters, or about 330 yards, of the lava flowing into the Pacific Ocean, the Coast Guard said in a statement on Monday. Previously, tourist boats with experienced professional captains could get permission to operate 50 meters or more away from the lava, but they will no longer be able to do so, said Matthew West, a Coast Guard spokesman.

The captain of the boat, Shane Turpin, said he was well outside the zone at the time of the explosion, Reuters reported on Tuesday. Mr. Turpin did not respond to a request for comment.

A video of an explosion that was captured from another lava tour boat around the time the boat was hit shows a huge plume of dark smoke and red lava on the water’s surface.

The Kilauea volcano erupted from its summit earlier this year after days of small earthquakes. The lava flow has destroyed hundreds of homes and other buildings, and the Hawaii County Civil Defense Agency urged tourists to steer clear of the area in May.