Stole this from an article:
Ocean worlds
"Water has more than a dozen solid states, only one of which is our familiar ice," says Frederic Pont of Geneva University. "Under very high pressure, water turns into other solid states denser than both ice and liquid water, just as carbon transforms into diamond under extreme pressures."
Hard for me to get my head around this. I can only picture the ice in my rum & coke. Just how many forms of solid water are there? Is the ice in my glass different than the ice in a glacier or iceberg? Any experts out there who can enlighten me?