A schoolboy drowned in a cave which was not difficult to explore but was prone to flooding, an inquest heard.
Tadcaster Grammar School pupil Joseph Lister died in Upper Nidderdale, North Yorkshire, on 14 November 2005.
The 14-year-old was learning caving techniques when he was thought to have been trapped by rising water levels.
Cave expert Alan Crossley told a jury at Harrogate Magistrates' Court that Manchester Hole, although safe, could flood in wet and windy conditions.
Mr Crossley told the inquest he had taken young children down the cave over many years with no difficulties.
But he said anyone exploring the cave system had to be wary of poor weather conditions.
"I check the reservoir on nearly every occasion"
Mr Crossley said the cave, which is 1,640ft (500m) long, was situated below two reservoirs.
Strong winds could force water over the top of one of the reservoirs and down towards Manchester Hole and another cave called Goyden Pot, he told the jury.
Mr Crossley said: "It hits Goyden Pot [the water] and backs up through that system and back up Manchester Hole."
"It is the significant wind factor that you are trying to avoid.
"I check the reservoir on nearly every occasion. I think it is essential you check the reservoir."
Joseph was exploring the cave with a group of fellow pupils when he became trapped.
Other pupils managed to escape, but Joseph's body was later recovered from the cave and taken to Harrogate District Hospital where he was pronounced dead.
The inquest is expected to last six days.
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