Such a tube would need to be pressurized to the depth of the deepest water. It would also block the flow of water through pinch points, deepening and accelerating that water. Where is this magic tube? Then imagine trying to handle this pressurized tube in not-deep and/or dry parts of the cave. It is pure fantasy.

A man died bringing an oxygen tank through this cave. Pulling 10,000lb rubber tube through that same hole?