I got stuck on step one: "secure hose to speaker". I'm reluctant to tape a hose to a paper-cone speaker, so I'm thinking I should use my ADAMs, whose woofers are a man-made composite and therefore more likely to be waterproof. Yeh, that's the ticket. Oh, wait -- they don't go down to 24Hz...I'll have to throw some water on the subwoofer and see if the cone dissolves.
When I was teaching electronics in another life, we used to do a demonstration wherein we'd modulate a Bunsen burner with audio (you need a tube amp for a high-voltage signal). Sound would come out of the flame! Very cool, even if not exactly hi-fi.