Bring your own bicycle/hiker's water bottle. The tap water on Bonaire is excellent, and not only is buying bottled water expensive, Bonaire then has the problem of the disposal of all those one-use, and then landfill plastic water bottles.
We bring Xstal Lite drink mix, or similar powdered mixes to avoid having to guess which mixes we will like when we go to the store. Also we bring small amounts of spices for cooking, rather than purchase larger containers on Island, which we will use very little of in a week.
BUG SPRAY. It was said earlier, but if mosquitoes find the taste of your skin appealing, sundown can make a nice dining experience a lot less enjoyable.
While many of the dive sites are similar, there is more of a variety than has been suggested. Double reef system to the south, with single reef system closer to town and to the north, and then further north in the Park area there is some steep volcanic rock rubble terrain. Even two dives in a row, on the same site often result in very different dives, as the reef is in constant change and you never know who/what you will see next.
The Eastern or Wild Side offers a less dived area, with usually larger life forms, and if you find the western sites too wimpy or easy to access, you can always do shore dives on the Wild Side. Like us you may have new scars to bring home and brag about from you Wild Side entries and exits! For the less adventurous, unwilling to roll around in fire coral and spiny urchins the Eastern side is serviced by boat.
I like the red eyes, as I get in a very full day of diving that first day, arriving early enough in the morning to register, eat breakfast, do the mandatory orientation, and get into the water. It pays to make sure that the resort you are using has a storage facility for your luggage if the room is not going to be ready that early, which is often true. Also a place to change so you can get into clean clothes, and swim suits, so you do not have to sit and wait for your room to be prepared.