how would I make hazard water that raises and lowers on a timed interval?

func_water_analog

cool, I didnt know it was so simple

BUT it has one BUT: The water will lose its shaders, so if you fall in, it will look just like above water, the fog is gone.

Am facing the same dilemma in my own map: moving water or realistic water? Aah, whatever, once you drop in you're dead anyway...

If you read the Valve developer wiki page, there are like 2 materials that were created specifically for water_analog that will keep their shaders.

yeah, but neither of them is toxic goo.

Possibly use the water_analog in combination with func_brushes that are disabled when the water moves?