Jana...
Your being beyond excited makes me excited for you. I love shipwrecks and they are what I dive mostly. I am not familiar with this shipwreck. I did a brief search and saw that the Sherman was a blockade runner and lies in about 50 fsw.
First and foremost make certain that you pay close attention to the captains dive brief that he or she will give before the dive. Other things I would encourage anyone to consider about diving a shipwreck include entries into and exits out of the water....especially your exits. With exits you may be dealing with ocean swells which may make exits a bit challenging.
You will most likely be doing ladder exits. Some ladders are closed on the ends and others are opened. The opened ones are called "fin friendly" ladders and are the best type for exits. I don't know if you are going on a larger or smaller dive boat. With the larger boats you will most likely be doing a giant stride entry and be doing a ladder exit. With a smaller boat you may be doing a back or side roll entry and your exit may require that you remove your gear then hop up on a platform.
A couple of things about exits and swells. Swells usually come in sets of 3. You want to grab the ladder in between sets. When you get to the ladder grab as high as you can then step onto it. If the ladder is fin friendly you simply slide your fins onto the rungs from the side. If it isn't fin friendly then you may be required to take your fins off first. If you get on the ladder and a swell comes before you get on the boat then bring your body up against the ladder and hang on tightly until you get between another set.
If someone is climbing the laddder ahead of you then keep a safe distance in case that diver falls back into the water. You don't want him or her falling on top of you. Keep your regulator in your mouth until you are safely on the boat. There may be no swells at all, but you are diving in the ocean and this will help you if there is a swell at the surface. Another issue is visibility. You may or may not have had experience with marginal visibility during your lake dives.
A dive on a wreck at this depth may have 20 feet of visibility or 50 feet...hopefully 50 feet when you dive it
I think the wreck is about 200 ft long. It is not a large wreck but you can see how you could easily lose direction with 20 feet of visibility. The captain will tie into the wreck and make sure you follow the anchor line to the wreck. They will most likely have a hang line at 15 feet that will run from the bow to the stern of the dive boat. The hang line will be tied into the anchor line on the bow. When you get in the water, head for the hang line and use it to get to the anchor line.
When you get to the wreck you will navigate using reference points. Swim a few yards and find a unique reference point then swim back to the anchor line. Swim back to the first reference point, go a few yards beyond that and locate another, etc...These features will
allow you to get back to the anchor line when you are ready to ascend. A compass will not be very reliable if there is alot of metal on the wreck.
If you have a larger swell on the surface then you will have surge on the wreck. A surge will pull and push you as the swells pass by on the surface. Surge can be substantial on any wreck but especially on a shallower wreck. Be careful swimming around big holes in the wreck if there are any because the surge can suck you inside the hole then push you up against the wreckage. It probably will not be that big of an issue, but being aware of it can keep you from getting beat up around the wreck.
Make sure you have some type of signaling device. A surface marker is a must and I would suggest you carry one with a spool line attached just in case you need to surface away from the anchor line. I also carry a whistle and mirror. Again...this is not likely to happen. The things I am writing about are simply devil's advocate considerations and will add to your safety by being knowledgeable and prepared.
A 3 mm wetsuit should be plenty for this time of year but I would encourage you to have a full suit as opposed to a shorty. There is the wreck itself and some marine life that can cause cuts and abrasions. I would also encourage a pair of gloves. They do not have to be expensive...just a basic glove will be fine.
Having a dive guide who has experience with the Sherman is always a plus...or simply diving with someone who is familiar with the wreck.
As with any dive, make sure you keep a close watch on your air pressure throughout the dive.
I promise you that your excitement is 100% warranted. It will be a wonderful and facinating adventure. Do not be surprised if your excitement after the dive exceeds that which you are feeling now. Have a great time!!!!
