Chloral hydrate. Quick, but mild.

Here's a magazine called Hydrate. It's 180 pages about water.

The hydrate is unusual in that it forms two different structures (both based on Mn(H2O)2F4 ), which have space groups P21 c and P21 a.

Direct injection of CO2 into the deep ocean is being considered for ocean depths greater than 500 metres, where CO2 may exist in liquid or solid gas hydrate form.143 The principal impact on mesopelagic and benthic ecosystems is likely to be reduced pH values and, for those organisms directly in the path of the CO2 plume, physiological stress caused by an elevated partial pressure of CO2.