The 75-year-old's body was found 100ft below the volcano crater rim about eight hours after his family reported him missing.
Water has been steadily rising in the pool since it was discovered at the end of July.
A green pond about the size of a pickup truck appeared at the bottom of the crater in July and it seems to be growing.
Hawaii Volcanoes National Park official said the man was taken to hospital for urgent care.
Hurricane Hector, which is moving west at 15 miles per hour, had sustained winds of 140 miles per hour on Sunday.
The volcano, which began erupting in May, has forced evacuations, destroyed homes and changed the island's landscape.
Chunks of Earth that float down the streams look like boats.
Coagulated volcanic spatter has created a 200 feet cone that should last for thousands of years.
Volcanic ash continued to sputter from a volcano on Hawaii's Big Island, raising health concerns about exposure to the toxic plumes.
Plumes of acid rain, vog and lava continue to plague Hawaii's Big Island.
Another small explosion occurred at Hawaii's Kilauea volcano Sunday morning, spewing ash plumes over Kau, the southernmost district of Big Island.
Images captured from a helicopter show seaside homes engulfed in flames as clouds of white steam and hydrochloric acid fumes billow from the water.
Hawaii's Kilauea Volcano has been erupting for four weeks, with no end in sight.
We've rounded up the 50 most spectacular photos of the past month, including a fiery Tesla crash, Real Madrid's Champions League victory and a terrifyingly realistic robot.
A tide of molten rock has turned residential streets in Hawaii into a volcanic wasteland as residents flee a surge of lava heading towards them.
Kīlauea has been particularly active over the past few weeks.
"Laze" is a combination of toxic hydrochloric acid fumes, steam and fine volcanic glass-like particles, which is formed when hot lava hits the ocean.
The fissure opened Sunday evening on private property near Halekamahina Loop Road.
Hawaii police said the man was also a suspect in another burglary case in Leilani Estates.
Beer and wine are still available as gift options at one store, but elsewhere little else is.