How would you script a muffled sound effect when underwater?

What I mean is that when the camera is directed underwater (I'm using smooth terrain) or inside of a block, all sounds have a muffled effect using the sound effect objects. This is similar to the sounds in the tunnels in Jailbreak and the water ROBLOXian Waterpark.

I am fairly new to scripting and I do not understand how you would achieve this. Would you insert the effect in every sound, disable it, then enable it when the camera is inside of it?

You can set SoundService's ReverbType's property to 'Underwater'

or

Use the FlangeSoundEffect and or the CompressorSoundEffect