It won't be a problem. Exactly where you will be depends upon which pier your boat uses.brianstclair:Hey boulderjohn, any idea if that timeframe (10:00 AM - 8:00 PM) seems reasonable to get a boat dive in? I have no idea how far the Caribbean piers are from the dive boats, or how far the dive boats are from the dive spots...
If you use the International pier (most likely), you will be right next to Dive with Martin, a pretty nice operator who gets a lot of good reports.
In any event, you won't be far away from anything. You will arrive too late for the morning trips, but you will be in plenty of time to get to any operator for an afternoon trip. A quick search of this site for recommended operators will give you a bunch of names, and you will be able to communcate with any of them ahead of time to via their web sites for their schedules.