var rb_timer, rb_top, rb_height, rb_jump = 4;

function scrollup() {
	rb_top = rb_top - rb_jump;
	if (-1*rb_top > rb_height)
		rb_top = $(".rb_c_shadow").height();
	$(".rb_swimmer").css("top", (rb_top + "px"));

}

$(document).ready(function(){
	$(".rb_c_shadow").hover(function() {
		rb_height = $(".rb_swimmer").height();
		rb_top = $(".rb_swimmer").css("top");
		rb_top = rb_top.substring(0, rb_top.indexOf("px"));
		rb_timer = setInterval("scrollup()", 5);
	}, function(){
		clearInterval(rb_timer);
	});
});