Волнистая форма с CSS

#wave {
  position: absolute;
  height: 70px;
  width: 600px;
  background: #e0efe3;
}

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

#wave {
  position: relative;
  height: 70px;
  width: 600px;
  background: #e0efe3;
}
#wave:before {
  content: "";
  display: block;
  position: absolute;
  border-radius: 100% 50%;
  width: 340px;
  height: 80px;
  background-color: white;
  right: -5px;
  top: 40px;
}
#wave:after {
  content: "";
  display: block;
  position: absolute;
  border-radius: 100% 50%;
  width: 300px;
  height: 70px;
  background-color: #e0efe3;
  left: 0;
  top: 27px;
}

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

svg {
  display: inline-block;
  position: absolute;
  top: 0;
  left: 0;
}
.container {
  display: inline-block;
  position: relative;
  width: 100%;
  padding-bottom: 100%;
  vertical-align: middle;
  overflow: hidden;
}

<div class="container">
  <svg viewBox="0 0 500 500" preserveAspectRatio="xMinYMin meet">
    <path d="M0,100 C150,200 350,0 500,100 L500,00 L0,0 Z" style="stroke: none; fill:red;"></path>
  </svg>
</div>

/** CSS using pseudo-elements: **/

#A {
  background: #0074D9;
}

#B {
  background: #7FDBFF;
}

#A::after {
  content: "";
  position: relative;
  left: -3rem;
  /* padding * -1 */
  top: calc( 3rem - 4rem / 2);
  /* padding - height/2 */
  float: left;
  display: block;
  height: 4rem;
  width: 100vw;
  background: hsla(0, 0%, 100%, 0.5);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 70 500 60' preserveAspectRatio='none'%3E%3Crect x='0' y='0' width='500' height='500' style='stroke: none; fill: %237FDBFF;' /%3E%3Cpath d='M0,100 C150,200 350,0 500,100 L500,00 L0,0 Z' style='stroke: none; fill: %230074D9;'%3E%3C/path%3E%3C/svg%3E");
  background-size: 100% 100%;
}


/** Cosmetics **/

* {
  margin: 0;
}

#A,
#B {
  padding: 3rem;
}

div {
  font-family: monospace;
  font-size: 1.2rem;
  line-height: 1.2;
}

#A {
  color: white;
}

<div id="A">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus nec quam tincidunt, iaculis mi non, hendrerit felis. Nulla pretium lectus et arcu tempus, quis luctus ex imperdiet. In facilisis nulla suscipit ornare finibus. …
</div>

<div id="B" class="wavy">… In iaculis fermentum lacus vel porttitor. Vestibulum congue elementum neque eget feugiat. Donec suscipit diam ligula, aliquam consequat tellus sagittis porttitor. Sed sodales leo nisl, ut consequat est ornare eleifend. Cras et semper mi, in porta nunc.</div>

 

function PolyCalc(f /*a function(t)  from [0, infinity) => [0, 1]*/, 
                  s, /*a slice function(y, i) from y [0,1] => [0, 1], with slice index, i, in [0, n]*/
									w /*window size in seconds*/,
                  n /*sample size*/,
                  o /*orientation => left/right/top/bottom - the 'flat edge' of the polygon*/ 
                  ) 
{
	this.polyStart = "polygon(";
  this.polyLeft = this.polyStart + "0% 0%, "; //starts in the top left corner
  this.polyRight = this.polyStart + "100% 0%, "; //starts in the top right corner
  this.polyTop = this.polyStart + "0% 0%, "; // starts in the top left corner
  this.polyBottom = this.polyStart + "0% 100%, ";//starts in the bottom left corner
  
  var self = this;
  self.mapFunc = s;
  this.func = f;
  this.window = w;
  this.count = n;
  var dt = w/n;  

  switch(o) {
    case "top":
      this.poly = this.polyTop; break;
    case "bottom":
      this.poly = this.polyBottom; break;
  	case "right":
    	this.poly = this.polyRight; break;
  	case "left":
  	default:
  		this.poly = this.polyLeft; break;
    }
    
  this.CalcPolygon = function(t) {
  	var p = this.poly;
    for (i = 0; i < this.count; i++) {
      x = 100 * i/(this.count-1.0);
      y = this.func(t + i*dt);
      if (typeof self.mapFunc !== 'undefined')
      	y=self.mapFunc(y, i);
      y*=100;
      switch(o) {
        case "top": 
          p += x + "% " + y + "%, "; break;
        case "bottom":
          p += x + "% " + (100-y) + "%, "; break;
      	case "right":
        	p += (100-y) + "% " + x + "%, "; break;
      	case "left":
        default:
        	p += y + "% " + x + "%, "; break;          
      }
    }
    
    switch(o) { 
      case "top":
        p += "100% 0%)"; break;
      case "bottom":
        p += "100% 100%)";
        break;
    	case "right":
      	p += "100% 100%)"; break;
    	case "left":
      default:
      	p += "0% 100%)"; break;
    }
    
    return p;
  }
};

var text = document.querySelector("#text");
var divs = document.querySelectorAll(".wave");
var freq=2*Math.PI; //angular frequency in radians/sec
var windowWidth = 1; //the time domain window which determines the range from [t, t+windowWidth] that will be evaluated to create the polygon
var sampleSize = 60;
divs.forEach(function(wave) {
  var loc = wave.classList[1];

  var polyCalc = new PolyCalc(
	  function(t) { //The time domain wave function
  	  return (Math.sin(freq * t) + 1)/2; //sine is [-1, -1], so we remap to [0,1]
    },
    function(y, i) { //slice function, takes the time domain result and the slice index and returns a new value in [0, 1]  
      return MapRange(y, 0.0, 1.0, 0.65, 1.0);  //Here we adjust the range of the wave to 'flatten' it out a bit.  We don't use the index in this case, since it is irrelevant
    },
    windowWidth, //1 second, which with an angular frequency of 2pi rads/sec will produce one full period.
    sampleSize, //the number of samples to make, the larger the number, the smoother the curve, but the more pionts in the final polygon
    loc //the location
  );
  
    var polyText = polyCalc.CalcPolygon(0);
    wave.style.clipPath = polyText;
    wave.style.shapeOutside = polyText;
    wave.addEventListener("click",function(e) {document.querySelector("#polygon").innerText = polyText;});
  });

function MapRange(value, min, max, newMin, newMax) {
  return value * (newMax - newMin)/(max-min) + newMin;
}

//Animation - animate the wave by uncommenting this section
//Also demonstrates a slice function which uses the index of the slice to alter the output for a dampening effect.
/*
var t = 0;
var speed = 1/180;

var polyTop = document.querySelector(".top");

var polyTopCalc = new PolyCalc(
	  function(t) {
  	  return (Math.sin(freq * t) + 1)/2;
    },
    function(y, i) {       
      return MapRange(y, 0.0, 1.0, (sampleSize-i)/sampleSize, 1.0);
    },
    windowWidth, sampleSize, "top"
  );

function animate() {
		var polyT = polyTopCalc.CalcPolygon(t);    
    t+= speed;
    polyTop.style.clipPath = polyT;    
    requestAnimationFrame(animate);
}

requestAnimationFrame(animate);
*/

div div {
  padding:10px;
  /*overflow:scroll;*/
}

.left {
  height:100%;
  width:35%;
  float:left;
}

.right {
  height:200px;
  width:35%;
  float:right;
}

.top { 
  width:100%;
  height: 200px;  
}

.bottom {
  width:100%;
  height:200px;
}

.green {
  background:linear-gradient(to bottom, #b4ddb4 0%,#83c783 17%,#52b152 33%,#008a00 67%,#005700 83%,#002400 100%); 
} 

.mainContainer {
  width:100%;
  float:left;
}

#polygon {
  padding-left:20px;
  margin-left:20px;
  width:100%;
}

<div class="mainContainer">

  <div class="wave top green">
    Click to see the polygon CSS
  </div>
  
  <!--div class="wave left green">
  </div-->
  <!--div class="wave right green">
  </div-->  
  <!--div class="wave bottom green"></div-->  
</div>
<div id="polygon"></div>