Wikipedia to the rescue (again) http://en.wikipedia.org/wiki/Alpheidae

It's not a stream of hot air, it's a stream of bubbles that can stun fish and break jars. Increase its size and you get a geyser of bubbles that can stun a person and possibly cause damage (probably be non-lethal damage). The force could move creatures back or even knock them down.

I've seen a previous version of this, didn't like it much though.

Debby