SVG filter ( liquid style )

index.html

<div id="wrapper">
  <div class="a"></div>
  <div class="b"></div>
</div>

  <svg>
  <defs>
    <filter id="goo">
      <feGaussianBlur in="SourceGraphic" stdDeviation="10" result="name" />
      <feColorMatrix in="name" mode="matrix" values="1 0 0 0 0
                                                     0 1 0 0 0
                                                     0 0 1 0 0
                                                     0 0 0 16 -8" 
      result="b" />
      <feBlend in="SourceGraphic" in2="b" />
    </filter>
  </defs>
  </svg>  
  

style.css

#wrapper {
  filter:url(#goo);
}