It might be more likely that the pressure is what is dangerous, essentially it wouldn't be dissimilar to an explosion.
My guess is that sound pressure is much more dangerous to humans when underwater because the medium the energy travels through is shared in the human body (being about 60% water overall) so the energy transfers more efficiently.
You'd be looking at organ ruptures or internal bleeding, instant deafness at the very least since the threshold for hearing damage is anything above 130Db for less than 1 second (and thats when sound is traveling through air).
Also decibels scale logarithmically meaning that the number doesn't represent a linear increase in energy (for example 20Db is around 10 times louder than 10Db).