It kind of depends on your definition of deepest cave :) It is usually taken to mean the greatest vertical distance from the cave mouth to its deepest explored point, so the deepest caves actually start pretty high up to begin with. The deepest known cave is Krubera in Georgia at over 2kms deep. It doesn't extend below sea level. However there may be other caves that are deeper, but not explored, and Krubera may well extend to below sea level, we just haven't found a way to get down that far (the limestone massif it is situated in extends below sea level and there have been tests releasing dye into the cave- the dye came out offshore in the black sea I believe).
There are plenty of caves that do extend below sea level- all sea caves will have done so at some point.
The voronja cave system.
Krubera Cave (aka Voronya Cave).
The deepest cave on the face of the earth is Krubera Cave, sometimes called Voronja Cave and is located in the Arabika Massif of the Gagrinsky Range of the Western Caucasus. It became recognized as the deepest cave in 2001 when the Ukrainian Speleological Association reached a depth of 5,610 ft., a deeper distance than the previous holder of that title, Lamprechtsofen in the Austrian Alps.
The Voronya cave and Vrtoglavica cave
ressseudufoillis
The Krubera-Voronja Cave is located in Abkhazia,Georgia.According to Geography it is also the deepest cave at 2191 meters!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
The deepest point in Carlsbad Cavern, the park's tour cave, is 1037 feet below the surface, or 0.196 miles. However, this area is not open to the public. The deepest point the public visits is about 830 feet underground.
The deepest point so far explored is 654 feet at the Wind Cave, in Wind Cave National Park, ND.
Cerulean Cave, Deepest point.
Mewtwo is in the deepest part of cerulean cave
He's on the lowest level, just keep heading down. I think it's two levels below the entrance level.
Nettle bed, outside of Motueka, Nelson