这么漂亮，怎么做的？一定要搞清楚！

就是Flash啊.
透明的Flashhttp://www.56kc.com/templet/56KC%20templet1.files/fish.swf
<div id="Layer1" style="position:absolute; left:0; top:0; width:100%; height:100%; z-index:7"> 
  <DIV id=Layer3 
style="Z-INDEX: 6; LEFT: 0px; VISIBILITY: visible; WIDTH: 100%; POSITION: absolute; TOP: 0px; HEIGHT: 100%"> 
    <OBJECT classid=clsid:D27CDB6E-AE6D-11cf-96B8-444553540000 
codeBase=http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,0,0 width="100%" 
height="100%">
    <PARAM NAME="_cx" VALUE="9499"><PARAM NAME="_cy" VALUE="8625"><PARAM NAME="FlashVars" VALUE="9499"><PARAM NAME="Movie" VALUE="56KC%20templet1.files/fish.swf"><PARAM NAME="Src" VALUE="56KC%20templet1.files/fish.swf"><PARAM NAME="WMode" VALUE="Transparent"><PARAM NAME="Play" VALUE="0"><PARAM NAME="Loop" VALUE="-1"><PARAM NAME="Quality" VALUE="High"><PARAM NAME="SAlign" VALUE=""><PARAM NAME="Menu" VALUE="-1"><PARAM NAME="Base" VALUE=""><PARAM NAME="AllowScriptAccess" VALUE="always"><PARAM NAME="DeviceFont" VALUE="0"><PARAM NAME="EmbedMovie" VALUE="0"><PARAM NAME="SWRemote" VALUE=""></OBJECT>
</DIV>
</div>