<!-- WATER - use turbulence -->
<feTurbulence type="turbulence" baseFrequency="0.01 0.1" />

<!-- CLOUDS - use fractalNoise -->
<feTurbulence type="fractalNoise" baseFrequency="0.01" />

Source -> feTurbulence -> feDisplacementMap -> feComponentTransfer -> feComposite
            (waves)        (distortion)         (color/opacity)      (blend)

<feTurbulence
  type="turbulence"           <!-- MUST be turbulence for water -->
  baseFrequency="0.01 0.1"    <!-- TWO values: x-freq y-freq -->
  numOctaves="3"              <!-- 2-5: wave complexity -->
  seed="42"                   <!-- Variation (free performance) -->
  result="waves"
/>

<feDisplacementMap
  in="SourceGraphic"          <!-- What gets distorted -->
  in2="waves"                 <!-- Distortion pattern (from turbulence) -->
  scale="20"                  <!-- 10-40 for realistic refraction -->
  xChannelSelector="R"        <!-- Which color channel drives X displacement -->
  yChannelSelector="G"        <!-- Which color channel drives Y displacement -->
  result="refracted"
/>

<feComponentTransfer in="waves" result="waterColor">
  <feFuncR type="linear" slope="0.3" intercept="0"/>     <!-- Reduce red -->
  <feFuncG type="linear" slope="0.7" intercept="0.2"/>   <!-- Boost green -->
  <feFuncB type="linear" slope="1.2" intercept="0.3"/>   <!-- Strong blue -->
  <feFuncA type="linear" slope="0.6" intercept="0.3"/>   <!-- Water opacity -->
</feComponentTransfer>

<feGaussianBlur
  in="waves"
  stdDeviation="2"            <!-- 1-5 for soft caustic patterns -->
  result="caustics"
/>

<feFlood flood-color="#0077be" flood-opacity="0.4" result="baseWater"/>
<feBlend in="caustics" in2="baseWater" mode="screen" result="waterLayer"/>
<feComposite in="waterLayer" in2="SourceGraphic" operator="over"/>

<svg width="100%" height="300">
  <defs>
    <filter id="oceanWaves" x="0" y="0" width="100%" height="100%">
      <feTurbulence type="turbulence"
                    baseFrequency="0.005 0.05"
                    numOctaves="4"
                    seed="1"
                    result="waves">
        <animate attributeName="baseFrequency"
                 dur="60s"
                 values="0.005 0.05;0.007 0.06;0.005 0.05"
                 repeatCount="indefinite"/>
      </feTurbulence>
      <feDisplacementMap in="SourceGraphic" in2="waves" scale="25"/>
    </filter>
  </defs>
  <rect width="100%" height="100%" fill="url(#oceanGradient)" filter="url(#oceanWaves)"/>
</svg>

<filter id="pondRipples">
  <feTurbulence type="turbulence"
                baseFrequency="0.02 0.02"  <!-- Equal = circular -->
                numOctaves="2"
                seed="10"
                result="ripples"/>
  <feDisplacementMap in="SourceGraphic" in2="ripples" scale="12"/>
</filter>

<filter id="shoreWaves">
  <feTurbulence type="turbulence"
                baseFrequency="0.008 0.12"  <!-- Strong vertical motion -->
                numOctaves="3"
                seed="5"
                result="waves"/>
  <feGaussianBlur in="waves" stdDeviation="1.5" result="softWaves"/>
  <feDisplacementMap in="SourceGraphic" in2="softWaves" scale="30"/>
  <!-- Add foam layer -->
  <feTurbulence type="fractalNoise"
                baseFrequency="0.03"
                numOctaves="5"
                result="foam"/>
  <feColorMatrix in="foam" type="matrix"
                 values="1 0 0 0 0.9
                         1 0 0 0 0.95
                         1 0 0 0 1
                         0 0 0 0.3 0"/>
</filter>

<filter id="underwater" x="-10%" y="-10%" width="120%" height="120%">
  <feTurbulence type="turbulence"
                baseFrequency="0.015 0.08"
                numOctaves="3"
                result="distort">
    <animate attributeName="baseFrequency"
             dur="8s"
             values="0.015 0.08;0.018 0.09;0.015 0.08"
             repeatCount="indefinite"/>
  </feTurbulence>
  <feDisplacementMap in="SourceGraphic" in2="distort"
                     scale="20"
                     xChannelSelector="R"
                     yChannelSelector="B"/>
  <!-- Slight blue tint -->
  <feColorMatrix type="matrix"
                 values="0.9 0 0 0 0
                         0 0.95 0 0 0.02
                         0 0 1.1 0 0.05
                         0 0 0 1 0"/>
</filter>

<filter id="liquidGlass" x="-5%" y="-5%" width="110%" height="110%">
  <feTurbulence type="turbulence"
                baseFrequency="0.01 0.05"
                numOctaves="2"
                seed="99"
                result="ripple">
    <animate attributeName="seed"
             dur="4s"
             values="99;100;101;100;99"
             repeatCount="indefinite"/>
  </feTurbulence>
  <feDisplacementMap in="SourceGraphic" in2="ripple" scale="8"/>
  <!-- Frosted glass blur -->
  <feGaussianBlur stdDeviation="0.5"/>
</filter>

<filter id="cartoonWater">
  <feTurbulence type="turbulence"
                baseFrequency="0.02 0.08"
                numOctaves="1"  <!-- Low octaves = bold shapes -->
                result="waves"/>
  <feDisplacementMap in="SourceGraphic" in2="waves" scale="15"/>
  <!-- Sharp edges, no blur -->
</filter>

const turbulence = document.querySelector('#seaFilter feTurbulence');
let frame = 0;

function animateWaves() {
  frame += 0.003;

  // Gentle breathing motion
  const xFreq = 0.006 + Math.sin(frame) * 0.002;
  const yFreq = 0.05 + Math.sin(frame * 0.7) * 0.01;

  turbulence.setAttribute('baseFrequency', `${xFreq} ${yFreq}`);
  requestAnimationFrame(animateWaves);
}

animateWaves();

<feTurbulence baseFrequency="0.01 0.1" numOctaves="3">
  <animate
    attributeName="baseFrequency"
    dur="60s"
    keyTimes="0;0.5;1"
    values="0.008 0.08;0.012 0.12;0.008 0.08"
    repeatCount="indefinite"
  />
</feTurbulence>

.wave-layer {
  animation: wave-drift 20s linear infinite;
}

@keyframes wave-drift {
  from { transform: translateX(0) translateY(0); }
  to { transform: translateX(-50%) translateY(5px); }
}

<feTurbulence baseFrequency="0.01 0.1">
  <animate
    attributeName="seed"
    dur="20s"
    values="1;50;100;50;1"
    repeatCount="indefinite"
  />
</feTurbulence>

<div class="ocean">
  <div class="wave wave-back"></div>
  <div class="wave wave-mid"></div>
  <div class="wave wave-front"></div>
  <div class="foam-layer"></div>
</div>

.ocean {
  position: relative;
  height: 100vh;
  background: linear-gradient(180deg,
    #0c4a6e 0%,
    #0369a1 40%,
    #0ea5e9 100%
  );
  overflow: hidden;
}

.wave {
  position: absolute;
  width: 200%;
  height: 100%;
  background: rgba(255,255,255,0.1);
}

.wave-back {
  filter: url(#waveBack);
  opacity: 0.3;
  animation: drift 90s linear infinite;
  bottom: 0;
}

.wave-mid {
  filter: url(#waveMid);
  opacity: 0.5;
  animation: drift 60s linear infinite;
  bottom: -5%;
}

.wave-front {
  filter: url(#waveFront);
  opacity: 0.7;
  animation: drift 35s linear infinite;
  bottom: -10%;
}

.foam-layer {
  position: absolute;
  bottom: 0;
  width: 100%;
  height: 20%;
  background: linear-gradient(to top,
    rgba(255,255,255,0.8) 0%,
    transparent 100%
  );
  filter: url(#foamFilter);
}

@keyframes drift {
  from { transform: translateX(0); }
  to { transform: translateX(-50%); }
}

.deep-ocean {
  background: linear-gradient(180deg,
    #0c4a6e 0%,    /* Deep blue */
    #075985 30%,
    #0369a1 60%,
    #0284c7 100%   /* Surface shimmer */
  );
}

.tropical {
  background: linear-gradient(180deg,
    #06b6d4 0%,    /* Cyan surface */
    #22d3ee 40%,
    #67e8f9 70%,
    #a5f3fc 100%   /* Shallow sand reflection */
  );
}

.stormy {
  background: linear-gradient(180deg,
    #1e293b 0%,    /* Dark clouds */
    #334155 30%,
    #475569 60%,
    #64748b 100%   /* Whitecaps */
  );
}

.sunset-water {
  background: linear-gradient(180deg,
    #831843 0%,    /* Pink sky */
    #9d174d 20%,
    #be185d 40%,
    #0369a1 60%,   /* Water starts */
    #0c4a6e 100%
  );
}

<!DOCTYPE html>
<html>
<head>
  <style>
    * { margin: 0; padding: 0; box-sizing: border-box; }

    .ocean-scene {
      position: relative;
      width: 100%;
      height: 100vh;
      background: linear-gradient(180deg,
        #87CEEB 0%,    /* Sky */
        #87CEEB 40%,
        #0369a1 40%,   /* Horizon */
        #0c4a6e 100%   /* Deep */
      );
      overflow: hidden;
    }

    .horizon-line {
      position: absolute;
      top: 40%;
      left: 0;
      right: 0;
      height: 2px;
      background: rgba(255,255,255,0.3);
    }

    .wave {
      position: absolute;
      width: 200%;
      height: 60%;
      bottom: 0;
      background: rgba(255,255,255,0.15);
    }

    .wave-1 {
      filter: url(#wave1);
      animation: drift 80s linear infinite;
      opacity: 0.4;
    }

    .wave-2 {
      filter: url(#wave2);
      animation: drift 55s linear infinite;
      animation-delay: -20s;
      opacity: 0.6;
    }

    .wave-3 {
      filter: url(#wave3);
      animation: drift 35s linear infinite;
      animation-delay: -10s;
      opacity: 0.8;
    }

    @keyframes drift {
      from { transform: translateX(0); }
      to { transform: translateX(-50%); }
    }
  </style>
</head>
<body>
  <svg style="position:absolute;width:0;height:0">
    <defs>
      <filter id="wave1" x="0" y="0" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.004 0.04" numOctaves="3" seed="1"/>
        <feDisplacementMap in="SourceGraphic" scale="15"/>
      </filter>
      <filter id="wave2" x="0" y="0" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.006 0.06" numOctaves="3" seed="2"/>
        <feDisplacementMap in="SourceGraphic" scale="20"/>
      </filter>
      <filter id="wave3" x="0" y="0" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.01 0.1" numOctaves="4" seed="3"/>
        <feDisplacementMap in="SourceGraphic" scale="25"/>
      </filter>
    </defs>
  </svg>

  <div class="ocean-scene">
    <div class="horizon-line"></div>
    <div class="wave wave-1"></div>
    <div class="wave wave-2"></div>
    <div class="wave wave-3"></div>
  </div>
</body>
</html>

<style>
  .underwater-container {
    position: relative;
    width: 100%;
    overflow: hidden;
  }

  .content-behind-water {
    /* Your actual content */
  }

  .water-overlay {
    position: absolute;
    inset: 0;
    pointer-events: none;
    filter: url(#underwaterDistort);
  }

  .caustics {
    position: absolute;
    inset: 0;
    background: url('data:image/svg+xml,...') repeat;
    opacity: 0.3;
    mix-blend-mode: overlay;
    animation: caustic-shift 10s linear infinite;
  }

  @keyframes caustic-shift {
    from { background-position: 0 0; }
    to { background-position: 100px 50px; }
  }
</style>

<svg style="display:none">
  <defs>
    <filter id="underwaterDistort" x="-10%" y="-10%" width="120%" height="120%">
      <feTurbulence id="underwaterTurb" type="turbulence"
                    baseFrequency="0.015 0.08" numOctaves="3"/>
      <feDisplacementMap in="SourceGraphic" scale="20"
                         xChannelSelector="R" yChannelSelector="B"/>
      <feColorMatrix type="matrix"
                     values="0.85 0 0 0 0
                             0 0.9 0 0 0.02
                             0 0 1.1 0 0.08
                             0 0 0 1 0"/>
    </filter>
  </defs>
</svg>

<script>
  // Animate underwater distortion
  const turb = document.getElementById('underwaterTurb');
  let frame = 0;

  function animate() {
    frame += 0.005;
    const xFreq = 0.015 + Math.sin(frame) * 0.003;
    const yFreq = 0.08 + Math.sin(frame * 0.7) * 0.01;
    turb.setAttribute('baseFrequency', `${xFreq} ${yFreq}`);
    requestAnimationFrame(animate);
  }
  animate();
</script>