for a platformer, how would this be possible so that when you jump in it, it makes a splash depending on how you jump in, move with you while you swim etc, im just curious on how this would be done, cause ive got no idea.
[Game design makes my brain feel like its gonna explode.]
It is easy to 'fake' water when it is in a standing pool; as long as you don't want to have it do any swell physics stuff like pouring out when a plug is removed, etc. Those are complicated. But for simple splash effects, you can just create active objects to the sides of your water that work as "splash sprites", which travel in both directions as little ripples (ideally, make it a ripple "generator" that creates progressively smaller waves for a short second). If you're really enterprising, you could make it somehow subtract from the water overlay to create the 'sin wave' effect instead of merely being laid on top (I am working on exactly this effect in the project I'm in).
So for example:
"Upon hero hitting water"
"Create 1x water ripple facing left"
"Create 1x water ripple facing right"
"Set Y position of ripples to Y(Water)"
When the player hits the water (assuming you're not using the built in platform movement, but even if you are you can add in little formulas to count individual X and Y movement speed), create 5 splash particles.
water particle value A=0;
set A=1
set X position to player (add in +random(6)-3 for a little bit of randomisation)
set Y position to water
set value B and C to the players X and Y movement speed
set value D to random(100).
Water particle count is >0;
add 1 to value D,
Set transparency to value D
set x position to current position+value B (divide by 2 or 3 to slow it down a little)
set y position to current position+value C*-1 (this is important, it inverts the particle direction so it doesnt just continue down through the water)
Water particle value D>128 OR water particle hits summot;
Destroy!
Ripple
If you want to just drag and drop an effect in, create a 5x4 (so long as it's a rectangle) Perspective object at each end of the players impact on the water. Have each piece move to a different side and subtract from the zoom value. Zoom value<0; destroy!
But that's a real cut and shut method, but it's nowhere near as CPU intensive as Phizzies version.
I'd write up a bit on them wooshy ripple things (like the ones you can just about see on http://www.youtube.com/watch?v=j--8iXVv2_U at 1:55?) but that's a lot more complex and not off the top of my head!