Your code is crappy and incomplete, learn Actionscript instead of copying some random code k?
onClipEvent(load){
grav = 0;
}
onClipEvent(enterFrame){
grav++;
_y += grav;
if(Key.isDown(65)){
setspeed = "walk";
}else{
setspeed = "run";
}
while(_root.ground.hitTest(_x, _y, true)){
djump = false;
tjump = false;
_y --;
grav = 0;
}
if(_root.water.hitTest(_x, _y, true)){
grav *= slow*1.25;
}else{
speed = setspeed;
}
}