How badly upset would you be if the bad weather cancelled your trip? KathyV noted places in that region known for sharks, and the farther southern places aren't it. Could be that your main options might come down to...
1.) Book the trip you want, be sure you bought trip insurance, accept that hurricane season could throw a wrench in things but your odds may not be bad.
2.) Book a trip for Bonaire or Curacao, and enjoy them for what they've got, rather than looking for the big stuff.
You might also want to broaden your field of view.
Consider a trip to Morehead City, North Carolina, for shark action (
Trip report). In an older post, Tortuga James made a post including this excerpt (in my report, you can click to expand Seasonal Patterns and find this):
"August- The summer doldrums set in. Diving is great and we have many calm, hot days. The biggest weather threats are now tropical storms. By the end of the month we are watching the tropics for approaching hurricanes.
September- Hurricane season is in full force. They say that during the season the weather is great unless there is a hurricane. Very true. Great diving, warm (almost hot) water and generally some of the best visibility of the year unless a storm has just passed. Risky but you could have some of the best dives of your life if you get lucky.
October- Storm season is winding down and the cold fronts are starting. SW winds before the fronts are a little stronger than in the spring, but it is the same process. Nice weather follows after the front is well on its way. Tropical lows and hurricanes can still impact the weather. Still some of the best diving of the year if you catch it right. Water temps are still in the high 70's.
November- Cold fronts control the weather. Locals love this time of year. The water is still warm and the air can be too on a lot of days. Some of my best trips have been Thanksgiving weekend."
Richard.