function swim() {
 if(document.getElementById) {
  var fishStyle = document.getElementById("fish").style
  var fish2Style = document.getElementById("fish2").style
  if(parseInt(fishStyle.left) < 220) {
   fishStyle.left = 1020
   fishStyle.top = 450
  }else{
   fishStyle.left = parseInt(fishStyle.left) - 8
   fishStyle.top = parseInt(fishStyle.top) - 2
  }
  if(parseInt(fish2Style.left) > 1000) {
   fish2Style.left = 200
   fish2Style.top = 250
   }
  else {
   fish2Style.left = parseInt(fish2Style.left) + 8
   fish2Style.top = parseInt(fish2Style.top) + 2
    } 
 }else if(document.all) {
  var fishStyle=window.document.all.fish.style
  if(fishStyle.posLeft < 220) {
   fishStyle.posLeft = 1020
   fishStyle.posTop = 450
  }else{
   fishStyle.posLeft -= 8
   fishStyle.posTop -= 2
  }
 }
}