img1 = new Image();
img1.src = "img/ingroundpool13.jpg";

img2 = new Image();
img2.src = "img/ingroundpool22.jpg";

img3 = new Image();
img3.src = "img/ingroundpool03.jpg";

function showPool(num) {
  document.bigpool.src = eval("img" + num + ".src");
}