What is a sea cucumber ?

In the movie jackass, the guys dived in the water and started masturbating sea cucumbers, the narrator said is was bad luck for them, what can sea cucumbers do actually to them, are they harmful or poisonous? This might be a discussing question, but please i was just wondering.|||Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. There are a number of holothurian ( /藢h蓲l蓹蕣藞胃j蕣蓹ri蓹n/) species and genera, many of which are targeted for human consumption. The harvested product is variously referred to as trepang, b锚che-de-mer or balate|||http://en.wikipedia.org/wiki/Sea_cucumbe鈥?/a>|||http://lmgtfy.com/?q=sea+cucumber