"Undersea volcano eruption lamp". How does it work?

This is a relatively new type of motion lamps. Here are two examples:

http://www.onlinesciencemall.com/Shop/Control/fp/SFV/30852/vpid/262...

http://www.hkoffer.com/undersea-volcano-eruption-lamp-p-782.html

With a search engine, you'll find more.

But how do they work? A water pump placed under the water? How did they hermetically seal it?

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Permalink Reply by Num Lock on September 26, 2010 at 11:59pm

An electromagnetic bump? Placed under water, but not sealed, with electrical contacts touching water? I wonder how such a device can work at all. Thanks for telling that they are so unreliable!
Btw, throwing away the complete units is unpractical, it would be nicer to salvage the power cord and LEDs (as far as i understand, they are color changing and have LEDs) first.