This thread has so far been mostly Southern Cal diving as you are from AZ, as one poster said the Great Lakes is a bring your own stuff diving and the US East Coast is also bring your own stuff, even water. On the East coast there are not many large boats except for some Florida, North Carolina, and some in NY/NJ.
If you were to dive out of New England expect to have a 25 to 40' boat that is just a taxi, that being no nothing (tanks, air, food, water, or bunks) except the ride to and from the dive site/wreck. A Typical day would to be loaded and off the dock by 7 or 8AM, diving about 2 hours later, a 2 hour SI, 2nd dive, and run for home which gets you back on the dock by around 4PM. Once the boat is unloaded some boats have bunks that can swing down but tend to be very narrow and there is no AC or mosquito netting. So, you would need to bring all your stuff including food and water for each day.
Normally, there will be no Dive Master to guide you and no one will be checking you air pressures etc when you get back. In other words from the time you leave the boat to the time you get back on you own and once back on the boat you will be expected to quickly gather and store your gear.
What you may see is a mate who goes in first to tie the anchor in unless there is a mooring where you will just be told that "The ocean is Open." Also, don't be surprised if the mate and/or captain make a dive during your SI. If the mate did a tie in he also most likely did a normal dive afterward, if so the normal way to tell the boat captain that the tie in is complete is to let a Styrofoam coffee cup go from the bottom, so you may hear "The cup is up" which means gear up and go diving. At the end of the day the mate may make his 2nd dive which at the end of he unties the anchor and rides it off the wreck and then comes up. Yes the mate is diving solo and don't be surprised if there are two or more solo divers on the boat.
Also, make sure you understand the cancellation policies for the shop/boat you are booking through.
Typically, if a dive is canceled by mechanical or weather problems there is a full refund
If the trip is canceled by the captain after leaving the dock but before the first dive there is a full refund
If the trip is canceled by the passengers before or after leaving the dock there is no refund
If the trip is canceled by the captain or passengers after the first dive there is no refund.
As the east coast can also get choppy quite quickly sea sickness is a big possibility. If you get sick and can't dive you still pay the fair and the boat can't run you back to the dock till the days charter is complete for all the passengers.
So, depending on where you are going always call ahead and make sure that you know what you need to bring and what services are offered.