On the Black Manta, t-shirts and shorts or bathing suits are the order of the day. Towels are provided. If I'm on board for 5 days, I'll wear flip flops to the boat and have one t-shirt & pair of u/w per day, 2 bathing suits and two shorts. I'll have suntan lotion, my own liquid soap/shampoo (although the boat provides another brand), sun glasses, a non-diving related book, my log books and dive cert. They have common medicine on board like sudafed and dramamine, if you need it. Bring some wine or liquor if you want. They sell beer, soft drinks and (sometimes) wine on board but you can bring some if you want (I would not bring beer or soda). They have plenty to eat but many people seem to like to also take on snacks for munching between meals (although there is always fruit, toast and other food provided). Don't forget camera gear and rechargable batteries. There are adapters on board but you might want to bring your own if you want to make sure you have one. They have a tendancy to disappear. The zillions of outlets on board are the 3-pin UK type / 240 volt. They also rent any dive gear you will likely need.
I hope that helps.
