div{
    width: 300px;
    height: 300px;
    border: 3px solid red;
    border-radius: 100%;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    margin: auto;
    animation: 2s waterDrop;
    animation-iteration-count: infinite;
}

@keyframes waterDrop {
    from{
        border: 3px solid red;
        transform: scale(1);
    }
    to{
        transform: scale(2);
        opacity: 0;
    }
}