Ice, and water.

What's the third?

The three forms (and they are different colors as well) are

1) Open Water

2) Slush (slightly lighter gray) it's so wet that snow melts on it.

3) Hard Ice with an inch of snow on top

maybe it's just 'cause I'm a Northerner that I consider slush and ice different!

There is a difference between slush and ice. Former Canadia agrees with you.

when the ice turns to slush

You could get really wet, and cold, fast.