<div class="wave"></div>
<div class="wave" style="--c: #E91E63"></div>

html,
body {
  margin: 0;
  height: 100%;
  display: flex;
  justify-content: center;
  flex-direction: column;
  align-items: center;
  background: aliceblue;
  gap: 15px;
}
.wave {
  width: 400px;
  height: 200px;
  outline: 2px dashed gray;
  --c: #2196f3;
  --w1: radial-gradient(100% 57% at top, #0000 100%, var(--c) 100.5%) no-repeat;
  --w2: radial-gradient(100% 57% at bottom, var(--c) 100%, #0000 100.5%)
    no-repeat;
  background: var(--w1), var(--w2), var(--w1), var(--w2);
  background-position-x: -200%, -100%, 0%, 100%;
  background-position-y: 100%;
  background-size: 50.5% 100%;
  animation: m 1s infinite linear;
}

@keyframes m {
  0%  {background-position-x:-200%, -100%, 0%, 100%}
  100%{background-position-x:  0%, 100%, 200%, 300%}
}