The diving there is great, and the period you're coming is excellent as well. What I would recommend, is either come at the beginning of the season (November) or at the end, March-April. it will be a lot quieter then than during the height of the season, and conditions are normally excellent. In November chances are there will be some waves, but normally the visibility is better than later on in the season (at the moment though the vis is also good), in March-April the seas are flat, but there is more plankton in the water, reducing the visibility, increasing the chances of manta rays/whale sharks.