Liveaboard crews in remote places will appreciate paperbacks and dvds of recently released movies that you leave behind. I left season 6 of CSI on an Aggressor and it was a huge hit with the crew. The more luxurious boats have anticipated most of your needs, so many of the suggestions above, while good, will not apply. Power strips, clothespins, coffee cups, and storage bins will all be supplied. I forgot my toothbrush once and the boat had one for me--that would have been a long week otherwise. I have never been on a liveaboard that didn't have seasickness medication, but I bring my own--you really want to start taking it before you set foot on the boat if you are likely to be affected. I will iterate the suggestion to bring enough bathing suits. Otherwise, bring your normal toiletries and gear, but be extra vigilant about bringing everything you need, because the gift shop is usually not an option.