I ran the Search and read a lot, I've talked with the agents, but I'm still concerned...
Not sure if you have already read it or not but if not - if you search under my login cindy0519 - you will find my (long/detailed) trip report on our Oct 4 BB's trip ("Finally- Our Blackbeard's trip report).
The bunk's were "cozy" at best and none of the bunks (either in the main section or in the bow) seemed to be any bigger than the others. We did not have any space below our bunk for storage and neither did any of the bunks in the main cabin. Can't speak for the two rooms in the bow as we did not go down into them. However, I believe the people across from us (in the mid section of the boat) did have a small space of this type. All the cabins were preassigned - so no seeking out the best cabin option was available.
I insist on putting on clean clothes everyday (even if just for a few minutes, love that "fresh, clean" smell) and had plenty of room for what I packed, so I wouldn't worry too much. The stop in Bimini will definately be a welcomed one since you can actually take a fresh water shower at the bathouse at Wench's in Bimini (as someone else pointed out take a towel to keep downstairs and a chamis type towel/s for on deck -worked out great for us!) this is also an excellent spot to shave if you are so inclined. We also took our Olympus C5050z outfit and our RoadStor (portable hard drive) on the trip and had no issues. We did however keep both down in our room when not in use, mostly for equipment safety reasons - but we never had any problems.
There is no nitrox capability on BB's, only air and on our trip we averaged 4 dives a day. I asked for smaller tanks when confirming our trip and was told that they only have 80's, so not sure about getting a larger tank.
Definately take fowl weather gear -we were going to leave ours behind and boy am I glad we did not! It came in VERY handy during the 8-10 ft seas during our crossing into Bimini. We arrived salt covered and cold in Bimini but relatively dry thanks to the foul weather gear, others on the boat without such gear were sea sick, wet and postively miserable. I know that BB's is offering a Freeport departure during the winter months - are you taking advantage of this or braving the crossing? If doing the crossing take lots of sea sick med's and start taking them the night before you depart, as this will give the med's time to work before you need them (and you will need them
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All in all, there are small inconviences, but you will have a great time and get in some great diving! The crew of the boat will do all they can to make it an enjoyable trip and are very accomidating when reasonable request are made. Enjoy your trip!