00:00This lake was believed to have no bottom.
00:03Divers went down, searching for the floor,
00:05and some never came back.
00:08Then scientists finally found the bottom,
00:11but what they discovered was even more disturbing.
00:14This is Lake Serichael, a deep blue sinkhole
00:18hidden in the mountains.
00:19It drops almost vertically for around 840 feet,
00:23with freezing water, toxic hydrogen sulfide,
00:26and underwater tunnels disappearing deep into the rock.
00:30For centuries, early instruments couldn't properly detect
00:33the floor, creating the legend of a bottomless lake.
00:36But the lake does have a bottom.
00:39The mystery is what lies beyond it.
00:43Divers have found submerged passages branching into the mountain,
00:47and some of them still haven't been fully explored.
00:50So this lake isn't endless.
00:52Its hidden cave system might be the real nightmare.
00:56Would you dive into it for one million dollars?
