It all depends on which rigs and what you intend to do. I've been on several in the western gulf that weren't in the advanced category, and others in nearby areas that definitely were well beyond the general level of "advanced."
Where you have a hard reachable bottom and minimal currents rig diving is as easy as it gets. Just remember that cross memebers covered with barnacles HURT when a wave drives you into them. When approaching a rig 10' of water over you is your friend and stay off the surface any where near the perimiter of the rig! Where you have NO bottom (some LA and MS rigs are in places where the water "just gets thicker") or one well out of a diver's reach combined with multiple water layers with varying vis from 0 to 200' on the same dive and multiple current speeds and directions with each layer it gets advanced pretty quickly. Couple that with hunting or any other activity and it can get way beyond advanced in a BIG hurry. I've seen 7 distinct layers of water, all moving in different directions at speeds difficult for a diver to swim against, in a dive of under 120' with no hard bottom. The fish were huge though, and we brought up several.
Check with the charters in the area you intend to dive and see what conditions normally are. Remember you ALWAYS have "option 2" of staying on deck if conditions don't suit you, even if it means paying for the taxi ride just to go watch. I've made that choice several times. Never disregard the "little voice" telling you to stay aboard the boat, or on the beach for that matter. You may not know the reason it's nagging you, but IT does! Every time I've ignored it in the last 35 years of diving I found out why it was there before the dive was over!
In general you should have your ballast & buoyancy control down pretty well before hitting a rig, as the neat stuff is NOT on the bottom!
FT
