Underwater effect

I’m looking for a convincing way to make my audio sound like it was recorded underwater.

Any tips?

What is the sound?
What’s the context of your question, is it for a theatrical production?

Freesound has some hydrophone recordings which you could emulate / incorporate … http://www.freesound.org/search/?q=hydrophone

If the sound source is out of the water the high frequencies will be cut (muffled) when the listener/microphone is submerged.

The idea is to modify speech for a machinma. This is the effect I’m hoping to imitate: http://www.youtube.com/watch?v=-Z4ElRy8b6w&t=3m39s

Thanks for the tips! =)

Use the Low Pass Filter (Effect menu) on your voice (add in some “blub blub” sounds) and mix in some water effects (as per Trebor’s suggestion).