I'm going on Jan 31, 2015. The very non-obvious prep-list is here:
Blackbeard's Cruises Liveaboard Equipment Checklist
The things that I count as important to notice are:
1) Rain-wear. They include "waterproof pants" in the list, I guess; my legs were waterproof last time I checked. The implication is that a fleece may be required.
2) Towels (plural); "we furnish the bedding but no towels". This always annoys me, having to bring a towel in baggage adds significantly to the weight. I guess we'll pack one, but I've often just purchased at the destination.
3) Night dive marker ("chemical light stick or suitable alternative, may be purchased on board".) I don't much like chem-sticks, they make me feel like a pre-teen, so I just carry a cheap marker light.
Their check-in email observes that suitcases can be checked at the dock, but everything I might leave in the suitcase seems to be required on the boat.
The list does not include "dry bag", but I will be packing a large backpack-style dry bag and everything we take on the boat (apart from our dive gear) will be inside it, including that damn towel. I actually take a couple of other dry bags as well; I pack a non-waterproofed kindle and a controller for an insulin pump and that stuff really benefits from dry-bag protection. Anyone with a non-waterproof cellphone, or an iPad, should think about the same thing.
On another thread I've seen people recommending all sorts of weird stuff, like clamps and surge protectors. I've got a powerful USB charger off Amazon and I'm trying to standardize on USB charging for everything. If that charger blows up I guess I have to borrow someone else's, I'm not packing either a surge protector or a portable generator.
My Canon PowerShot D30 (82ft) needs it's own charger (annoying) and my SeaLife light does too (very annoying), but apart from that everything is USB.
On a previous liveaboard I found that my dive watch only stores 12 dives; only afterward, when I tried to download all the dives and found the early ones had disappeared. These days I carry a USB OTG adapter and download dives to my cellphone and that's worked pretty well over several dive trips.