PRAGUE (REUTERS) - Czech divers are preparing to search the world's deepest underwater cave again to see if there is more to be discoverer from its already record-breaking depths.

Last September, researchers identified the flooded limestone cave, called Hranicka Propast (Hranice Abyss) and located 300km east from Prague, as the deepest of its kind when they reached 404m below Earth's surface.

Access to the underwater part of the cave is inside a gorge nestled within a forest.

Exploration was halted then because the cord of a submersible robot used for the expedition was not enough to reach the bottom of the cave, Michal Guba from the Czech Speleological Society said.

The mini-submarine got then tangled in its cords on its way up and it has remained in the water, diver David Cani said, adding it could be hopefully retrieved in April.

The cave, which has become tourist attraction, is not accessible during winter.

Cani went only as deep as 200m, leaving the rest of the journey to a robot.

"It is dark, gloomy there, but I had a euphoric feeling when I got there," he said, referring the complete darkness of the underwater cave. "The rock (of the cave) goes 1.2km deep, (but) if we reach 500m, we will be happy too."

Until now, Italy's Pozzo del Merro was considered the world's deepest flooded cave at 392m.