Guess it depends on how fashionable you want to be.
I had 2 categories of clothing....wet and dry. I had 1 pair of shorts that I wore during the day while I was wet (over my swimsuit sometimes), and a second (nicer) pair that I wore after showering, during dinner and the evenings (for 3 hours). I wound up with 2 "wet" t-shirts and 2 dry ones. Didn't bother with shoes except for embarking and disembarking. You're going to want at least 2 swimsuits, though some folks on our boat had 3 or 4. I took 2 and wore one all morning, changing into my dry suit at lunch (when it was a longer SI) for our afternoon dives, then showered and put on dry clothes before dinner (I don't night dive). If you night dive, bring 3 suits (minimum) so you can put on a dry suit for dinner.
Big hint would be to make sure you have some kind of a cover-up that you can wear. I have a big Chammyz shirt with a hood that came in big time handy on our Belize itinerary. Even with the air temps being in the 80's, with the trade winds it's easy to get chilled after diving when your body temp is slightly down anyway. I bought my Chammyz especially for this trip and now won't do a charter without it (we only dive warm). Oh, but if you do consider buying one, keep in mind they run HUGE. I got a "fits most everyone" and it's even too big for my 6'4", 220# husband!!
You'll definitely want a hat to cover your salty hair during the day so the sun doesn't fry it even more. Keep in mind that nobody pays attention to what you're wearing, so pack light and plan on wearing things more than once. Oh yeah, and if you're on a liveaboard that has small cabins or bunks, pack even lighter. We were on the Nekton Pilot and had huge ensuite cabins with plenty of storage, but still packed light.
Oh yeah, bring EAR DROPS! I now carry them on all of our dive trips, not just liveaboards. With your ears getting wet 4-5x a day, you'll want something that can dry them out and sterlize them in the evenings.