Bonaire is known as a diver's paradise. For those of you who have non-diving family/friends, do not hesitate to take them to Bonaire. From this snorkeler's perspective, I can say with certainty that staying at the surface will not disappoint.
Other than possibly frog fish, sea horses and flamingo tongues, I have seen the same marine life as my diving friends. The variety of fish, both juvenile and adult, is the best in the eastern Caribbean. Trunkfish, parrotfish, grouper, black durgon, file fish, blennies, porcupines, rays, lobster, and so very many more. Add in a turtle, octopus, and some christmas tree worms and you have heaven under water.
The condition of the reef varies by dive site. Both hard and soft corals thrive in the waters of Bonaire. Some areas have little to no healthy reef while others are alive and full. In my experience, those spots that are not doing as well with reef still often have an abundance of fish activity.
In most cases, the dive/snorkel sites are easily accessible from shore. Hard soled dive booties with open back fins are essential as the shoreline is mostly rocky and/or broken corals. The ease/difficulty of entry is a varied as the marine life. Bonaire Shore Diving Made Easy by Susan Porter is very helpful in determining the best entry points.
A rental truck is needed to explore the shore sites lining the island's west coast. With the island being only 11 square miles, one can easily explore both southern and northern sites in the same day. If you are in the mood for a boat dive, a trip to Klein Bonaire is well worth it. The reef at Klein is in wonderful condition and is teeming with marine life.
In terms of water, I have traveled to Bonaire in late spring and fall and found the temperature to be comfortable with a rash guard. From my perspective the water is mostly clear, with the odd day of lower visibility. At Hilma Hooker, a cargo ship sitting at 95-100 feet, I was able to see the ship from the surface the day I was at that site.
As to chop and current, I find that the northern sites are best visited in the morning while the southern sites have been generally calmer at any time of day. I have personally never experienced a current so strong that I was not able to safely snorkel. There are a few places to do a drift dive/snorkel, Klein being one. Having said that, divers and snorkelers know conditions are always something to consider before going to any site and checking with the local dive operator is a good idea before setting off.
The island itself has a laid-back, easy-going feel. This is not the traffic jams and red lights of a place like Aruba. In fact, the worst traffic jam one is likely to encounter on Bonaire involves goats and wild donkeys. While the island is small in area and population, one can still find all one needs for a great vacation - friendly people, good restaurants, many grocery stores for self-catering, shopping if you so desire, land activities such as hiking, caving, and Harley rentals, and fantastic water.
Whether you are a diver or snorkeler, young or old, Bonaire is a great place for a vacation at any time of year.