.swim-container {
    display: block;
    position: relative;
    height: auto!important;
}

.swim-container img {
}

.swim-container > img:first-child {
    opacity: 1;
    transition: all .7s;
    z-index: 1;
    position: absolute;
    top: 0;
    left: 0;
    display: block;
    max-width: 100%;
    height: auto;

    
}

.swim-container:hover > img:first-child {
    opacity: 0;
    transition: all .7s
}