SOURCE

<div id="container">
    <div class="wave"></div>
</div>

   #container{
        width:400px;
        height:200px;
        position: relative;
        border:1px solid #ccc;
        margin:300px auto;
        overflow: hidden;
        background:seagreen;
    }
    .wave{
        background:#fff;
        border-radius:32%;
        width:500px;
        height:500px;
        position:absolute;
        left:50%;
        bottom:68px;
        animation: go 8s infinite linear;
    }
    @keyframes go {
        0% {
            transform: translate(-50%, 0) rotateZ(0deg);
        }
        50% {
            transform: translate(-50%, -2%) rotateZ(180deg);
        }
        100% {
            transform: translate(-50%, 0%) rotateZ(360deg);
        }
    }