After traveling with dive groups and living/working in the islands I find the diving culture (learned behavior) rather odd. Here is what I mean - people will wake up early in the morning to get on the boat to go diving, relax in the afternoon perhaps some shopping, then go out for dinner and party into the late hours of the night. Then they wake up early in the morning, tired from a lack of sleep and in many cases hung over from the night before, and go diving. The cycle is then repeated. This culture is prevalent within the diving community.
Why not sleep in during the morning, wake up and have a relaxing breakfast, go dive in the afternoon during the hottest part of the day, after returning take a nice shower and go do whatever (relax at the pool, shopping, etc.), go out to dinner and then party, if you are into it.
The recommendation isn't for everyone, however, I have noticed a tendency of people 'having' to dive in the morning, without out taking any consideration why, even if they are tired and/or hungover. When I ask people why they follow this learned behavior the most common answer is "I haven't really thought about it...it seems everyone else dives in the morning."
As mentioned above in a previous post, the afternoon dives are not any better or any worse than the morning dives. Pick a schedule that you would prefer rather than following the learned behavior without any thought. After all, you are on vacation. Enjoy and safe diving.