NICKY MILNE IN a small boat off the coast of Madagascar, Idrissa Tsirvelo struggled with a spanner on his rusted dive cylinder, then put a regulator in his mouth and disappeared under the water, risking death illegally harvesting sea cucumbers from the ocean floor. Deep sea diving for the worm-like marine animals - a delicacy selling for hundreds of dollars in Asia - can lead to death, injury or paralysis, but many young men in the Indian Ocean island say they have no other means of survival. "This work really scares me," said Tsirvelo. "As humans we are not meant…