.water-container {position:relative;width:200px;height:200px;background-color:#0099cc;overflow:hidden;} .water {position:absolute;bottom:0;width:100%;height:50px;background-color:#66ccff;animation:waterAnimation 2s infinite cubic-bezier(0.4,0.0,0.2,1);} @keyframes waterAnimation {0%,100% {transform:translateY(0);} 50% {transform:translateY(-20px);}}