Kind of a deathtrap
I want water to be under the player. Then (when triggered) the water will start rising and the player has to jump onto a platform. And the water stops rising so the player doesnt get hurt.
In other words.
A brush with toxic texture
A Trigger_hurt parented to the toxic brush
An entity to make it rise
How do i make the water rise?
I tried func_tracktrain. It just got very weird... somehow i cant make tracktrain go vertical.
I tried func_door and the same happened as with the tracktrain
'Water' + 'moving' doesn't go very well together. However a func_water_analog could be what you are looking for.
Please note: I haven't made a func_water_analog in Portal2, so I have no guarantees that it works. In HL2 there was only one texture you could use (maybe 2, not sure) for rising water. Even then the entity was incredibly buggy.
EDIT: I remember in this thread there was a small discussion about rising water. Research!
Actually i found an alternative. Why bring the water to you if you can bring yourself to the water? 
Moving the world can be just as annoying to work with.
I remember Omnicoder did a cool fall scene in one of his maps that mimic'd the player falling/objects falling with the player.
Why I thought of this and why I thought it was relevant... meh.
Perhaps mimicking water rising instead of actually having rising water would probably be a better option.
Yea Meh i made the deathtrap a little different... The water isnt coming up to you... the floor is moving away so you fall down 
I used a func_door clip brush with a door parented to it to move it up, maybe make a toxic brush with func_door tied to it and have the trigger_hurt parented to it? I know you have an alternative way, but I'm just throwing ideas out there.
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Yup i tried that 
tying water func_door just messes it really much up
What if you left the water where it was but moved the entire room downwards, thus giving the impression the water is rising.
I think in terms of boolean variables. Generally, it makes things easier.
Hah yes thats a Nice idea I was thinking, Can you parent instances?
I dont think so, unfortunately.
I think in terms of boolean variables. Generally, it makes things easier.