body {
  background-color: yellow;
  position: relative;
  margin: 0;
}

body::before {
    content: '';
    position: fixed;
    left: 0;
    top: 0;
    width: 150px;
    height: 100%;
    background-image: url('fish.gif');
    background-repeat: repeat-y;
    background-size: contain;
    z-index: 0;
}

body::after {
    content: '';
    position: fixed;
    right: 0;
    top: 0;
    width: 150px;
    height: 100%;
    background-image: url('fish.gif');
    background-repeat: repeat-y;
    background-size: contain;
    z-index: 0;
}

.opening {
    border: 20px ridge red;
    background-color: white;
    font-family: comic sans ms;
    font-size: 32px;
    width: 800px;
    z-index: 1;
} 
.paragraph {
    border: 20px ridge blue;
    background-color: white;
    font-family: comic sans ms;
    font-size: 16px;
    width: 800px;
    z-index: 1;
}