I would think that you would not need reservations too far in advance, but if you're going on Passaat, recognize that it is not a party barge like a lot of them, and they only carry a few passengers. I might think about doing a reservation maybe a couple weeks in advance. Haven't been on it myself, so not exactly sure on the snacks. Casual dress for sure, although I have had some ladies comment that you need to be careful not to wear high heels, as you have to get in and out of the dinghy to get to the boat, again, if you're doing Passaat.