As everyone knows, this is the shores of the Dead Sea: 430 m below sea level.
But what if we allow the deepest parts of deep lakes? The Dead Sea has a maximum depth of 304 m, which thus is 734 m (2408 ft) below sea level.
Lake Baikal - the largest (by volume), oldest and deepest lake in the world, has its surface at 455 m and a max depth of 1642 m, making its lowest point 1187 m (3894 ft) below sea level.
Glaciers can do amazing things: plenty of glacially carved lakes extend well below sea level. Patagonina (where I’m currently located) has O’Higgins/San Martín Lake, with surface at 250 m and max depth of 836 m. Might there be some lakes-under-construction, say in Greenland or Antarctica, that could exceed Lake Baikal?
It’s hard to tell exactly since it’s covered by almost four kilometers of ice, but some estimates say the bottom of Lake Vostok may be deeper than Baikal.
The current candidate mot likely is: Denman Glacier in East Antarctica
The BedMachine Antarctica map has estimated that the deepest canyon on Earth’s surface, plunging 3.5 kilometers below sea level, is under Denman Glacier in East Antarctica, nearly half as deep as Mount Everest is tall.