Just heard of the concept today after fish for the majority of my life. Does this technique actually help the fish? It'd seem dangerous, as your just letting water freely roam the bladder of the fish, forcing it to sink to an unsafe depth for that fish. One of my dreams is to go salt water fishing one of these days, and as I was reading the TPWD website about this technique (which they call "Depressurizing), I was dumbfounded by this.

I'm opposed to 'fizzing' fish caught at depths. You're poking a hole in their side that allows infection to take hold & kill them.

Here's a really, REALLY good discussion about deep-water release methods. The problems associated with releasing Gulf red snapper are comparable to the rockfish in the article.

http://www.adfg.alaska.gov/index.cfm?adfg=fishingsportfishinginfo.rockfishconservation

If you use a medical needle that comes on a syringe you will not have any issues with infection. Problem solved. You can get needles from Walgreens or CVS. Use them once and throw them away if you consistently catching deep and releasing and are worried about them dying.

As to whether it helps the fish or not is debatable. however, you are not letting any water in the fish's bladder, you are releasing air from the bladder through a small hole that seals itself back up. I'm not sure there is an unsafe depth for most fish until you get in the thousands of feet, but you just release the air, release the fish and let it swim to the depth it wants to. Remember, in Federal waters you have to have the gear (needle, etc) on board and use some sort of technique to depressurize the fish. It's the law.

The way you have to look at it is if you vent them they at least have a fighting chance for the wound to heal and then to survive, if you choose not to vent them they have probably a 5-10% chance of survival in opposition to a 70-80% chance if you vent them

Ah, but if you DON'T vent them, and instead use a fish descender device, the survival odds go up to as much as 98%.

I'm with zeek on this. I've seen that concept in action. it works, but it is not a viable solution on a Texas headboat situation.
on a headboat, the venting method is best. Texas sea center will send you a free one.
needle needs to have a pretty sizeable diameter to make it work correctly, without clogging. fish's slime coat covers the hole on exit, just clear & sterilize with alcohol between fish.
Don't count on the deckhands knowing, or even caring about the right way to do it, I've seen them stab 'em with a knife & chuck 'em back- not exactly surviveable.