[qjz]

This reminds me of Vonnegut's Ice-nine, but in the inverse. Drop one in the ocean and watch it disappear in a puff of gas.

"Science is magic that works." -- obligatory quote from Cat's Cradle

[wcoenen]

Then you might be interesting in reading about this synthetic biology project to engineer an organism that can be used to inhibit or stimulate the freezing of water:

http://2011.igem.org/Team:KULeuven

http://2011.igem.org/Team:KULeuven/Project