WaveScript

//Creation expression
vector $ppos = spray_particleShape.position;
float $pu = $ppos.x;
float $pv = $ppos.z;

float $offsetU = 0.5; // center (in X) of bounding box of emitting surface
float $offsetV = 0.5; // center (in Z) of bounding box of emitting surface
float $scaleU = 5; // width of bounding box of emitting surface
float $scaleV = 5; // depth of bounding box of emitting surface thanks to mduvekot on cgTalk

float $samp[] = `colorAtPoint -o RGBA -u $pu -v $pv `wave_deformationFile`;
float $py = $samp[0];
float $sprayStart = 0.6;

spray_particleShape.position = <<$ppos.x, $py, $ppos.z>>;
spray_particleShape.rgbPP = <<$samp[0], $samp[1], $samp[2]>>;

if ($py < $sprayStart){
	spray_particleShape.lifespanPP = 0;
}else{
	spray_particleShape.lifespanPP = 1;
}

// runtime contained a similar expression to make sure the particles floated on top of the waves on landing and didn't fly through them.