This is from a word doc I did for a first-timer some time ago. Therefore, some references are out-dated, i.e. Chat-n-Browse. This was cut-and-pasted, so forgive the ugly formatting...
Diving
Im assuming you are going to have a truck and plan on doing primarily/exclusively shore dives. The Island is oriented North/South, with most of the diving done on the west (lee) shore. When I say North below I mean the north end of the west side and likewise south end of the west side.
There are three distinct zones on Bonaire:
1. East (wild) side Ive never dove the east side, so cant say anything about it. Some dive ops run boats to the east side, and a couple of ops run guided shore dives (VIP and Wannadive, I think). It looks too much like work to me, and there is just too much easy, good diving on the west side.
2. North Drop off starts close to shore, mostly really easy entries. One thing to keep in mind: The road past 1000 Steps turns to one-way north bound. This means if you go to Ol Blue, Karpata, etc. then you must return via Rincon. When go up there we take lots of tanks and make a day of it. There is a short-cut dirt road over the mountain that gets you back on the two-way road, it used to be a goat-track, but they say it is improved.
3. South Longer swims out over a sandy bottom to the reefs. By long I mean a couple hundred yards. We do it as a surface swim, then drop on the reef. Return is done underneath because we get an extended safety stop, and sometimes there are cool creatures in the sand. Some sites in the south also have a double reef, that is a shallow reef topping out at about 30-40 ft, a sand valley, then a second reef topping out at about 60 ft.
Since Im directionally challenged: I define North as the center of Kralendijk thru the Slaagbai Park. South is the center of Kralendijk to the Willemstoren Lighthouse.
Winds from the south means limited site selection (windsock, and those right along there), or maybe the ones in town, from the Plaza up to about Yacht Harbor, and maybe the northern hotel/resort sites.
Winds from the east (normal) go anywhere north or south.
Winds from the west (very abnormal when weve been there), sleep in, recline in a lounge chair, drink beer. Or book a boat trip to the east side. Ive heard of people who shore dive the east when the wind is out of the west. I havent done either of those things, so dont know about it.
Boats to Klein Bonaire can usually find a lee without regard to wind direction.
There is a book called Bonaire Shore Diving Made Easy. It is available at almost any dive store on Bon. Theyll probably have it at BD. If not, walk next door. Buy it if you dont already have it. About $15 I think. At the worst, go to Chat n Browse, theyll have it.
Entries and Exits
Dont get hung up on the difficulty of this. Its not. Our first trip my two daughters were 12 & 13, and both had absolutely no difficulty on any of the dives we did.
The northern sites are characterized by dirt/rock paths down to the waters edge, then entry thru coral rubble that has a tendency to shift under your feet. Once youre in the water it is mostly sandy, with a few exceptions.
On most of the way-southern sites the entry is ironshore with a stepdown to sand/rock.
At some of the marked sites the dive ops have marked the best entry/exit spots with a pair of painted rocks. Go in between the markers easiest, and confines damage.
Back your truck as close as you can to the entry, gear up on the tailgate. Carry your fins and wade in until about waist/chest deep, put on fins and go. I usually get in first, out first so I can give my bride a hand if she needs it. Also, dont hesitate once you start in/out just go. Dont hurry, but dont stop either. I try to plan where Im putting my feet before I ever start, sometimes even do a trial run without gear. There will probably be big rocks and holes to trip you, so slide your feet and move on out to deeper water.
If it looks too rough, just go somewhere else no sense in getting beat up.
Navigation and the reefs
The reefs run parallel to the shore, and start in about 30 of water. The drop-off is fairly steep, but not a wall, down to about 100-130 to a sandy bottom. At some sites in the south, there is a double reef, that is, another reef that parallels shore past a sandy flat. We almost never go to the second reef, too far to swim. You probably should, at least once so you can say you did. Take a compass heading (sometimes vis is not good enough to see across the chute) and strike out.
Heres how we actually do a dive, north or south:
Im an anally retentive engineer, so I like to return to the same spot I left from. Besides pleasing me, it amazes my children that we can swim around (seemingly) randomly for an hour, then surface at exactly the spot we started from.
I stand on shore and take a compass heading perpendicular to the shore line. Sometimes there are buoys (dive boats tie up to them) that you can use as a target. Get in, then surface swim out on the compass heading. I lay on my back and use a marker on shore to counteract drift/surface currents. Once youre out as far as you want (to the edge of the reef) we descend and I find a marker (Ive seen people use a fishing float with a short piece of line tied to a weight) - some prominent topo feature (coral head, sponges, etc) at 30ish ft.
On our return I find this marker and then turn toward shore on the reciprocal compass heading. Once we descend, I check the current (it will run parallel to the reefs/shore, usually weakly) and head into it at whatever depth you like. We generally keep it pretty shallow, 40-60 ft. After about ½ the air is gone, or I get cold, we turn, ascend to 30 ft or so, and ride the current back to my marker, turn and head in. We go in on the bottom following the compass heading. There is a good opportunity to see octopi, eagle rays, peacock flounder, etc. in the sand flats, and you get a good safety stop. Its not uncommon for our dives to exceed an hour in duration.
Like I said, this is how we do it. Other people go until theyre ready to quit, surface, look around and swim back to the truck. Or go until theyre ready to quit, swim to shore, leave the gear and send somebody back to get the truck. Whatever works for you.